unit 2 heredity: inheritance and variation
TRANSCRIPT
Essential Questions 4
Lesson 2.1: Genes 5
Objectives Warm-up Learn about It Key Points Web Links Check Your Understanding Challenge Yourself
5 5 6
Lesson 2.2: Laws of Heredity and the Punnett Square 14
Objectives Warm-up Learn about It Key Points Web Links Check Your Understanding Challenge Yourself
14 14 15 27 27 28 29
Lesson 2.3: Non-Mendelian Inheritance 30
Objectives Warm-up Learn about It Key Points Web Links Check Your Understanding Challenge Yourself
30 30 31 40 40 40 42
Lesson 2.4: Multiple Genes 43
Objectives Warm-up Learn about It Key Points Web Links Check Your Understanding Challenge Yourself
43 43 44 46 46 46 47
Laboratory Activity 48
Performance Task 50
Self Check 52
Key Words 52
Wrap up 54
At the end of this unit, you should be able to answer the following questions. How are genes related to heredity? Why are genes important to human beings and other living organisms? How can the structure of genes affect the amino acid sequences? How were the pea plants used to generate the Mendelian laws? How are Punnett squares used to solve genetic problems? How did non-Mendelian patterns of inheritance occur? How are Mendelian laws different from non-Mendelian inheritance? Why is the environment a significant factor for traits considered under
multiple genes?
The deoxyribonucleic acid (or DNA) is the molecule responsible for carrying the genetic blueprint for the general identity of living organisms.
During meiosis, DNA is replicated, and the recombination between pairs of homologous chromosomes happen. Meiosis allows the exchange of genetic materials between chromosomes, leading to variations in the genetic makeup of the resulting haploid daughter cells. These haploid daughter cells are the gametes or sex cells.
Have you ever observed yourself in a mirror and wondered why you are the way you are? Or maybe, you have been fascinated at times, at how you are almost a carbon copy of your father, your mother, or a relative? Most of the times, people will tell you that you have the same traits as your parents because they passed their genes to you. What are genes, why are they important, and how do they affect you?
The Folk Hunt In this activity, you will roam around the room and guess whose parents are indicated in the picture. Materials:
picture of parents notebook
Procedure:
1. Have tables in a circle formation. 2. Take note of the letter that is assigned to you by your teacher. 3. Make sure to keep the photos of your parents hidden from your classmates
and indicate your assigned letter.
4. Randomly put the picture of your parents in different tables. 5. For five minutes, you will roam around the room and guess whose parents
are placed on the tables. Remember to indicate the letter for each picture that you are guessing.
Guide Questions:
1. How were you able to identify the parents of your classmates without meeting them?
2. What are the things that you have considered to accomplish the activity?
The gene consists of a specific nucleotide sequence and has a definite position in a given chromosome. This particular sequence codes for a specific protein for phenotype expression. A gene has four major units.
Exons are the coding regions, which are translated to a specific sequence of amino acids
Introns are the non-coding regions, which do not specify any amino acid sequence for protein synthesis.
The promoter region is the regulatory sequence that regulates the activation of genes, which also determines when and where the protein should be synthesized. The CAT and TATA boxes are components that are found in the promoter region.
Fig. 4. Chromosomes, DNA, and genes
Do not confuse chromosome with chromatin and chromatid. The chromosome is just the condensed version of chromatin. It means that chromatin is only evident during prophase while chromosome is evident during metaphase. The one that you can see in the microscope is chromosome, not chromatin. On the other hand, the chromatid is one version of the duplicated chromosome. Since there are 46 chromosomes in humans, the number of chromatids is 92. To help you remember the difference, bear in mind that a chromosome is also the same as sister chromatids.
Fig. 5. Difference of chromatin, chromatid, and chromosome.
Fig. 6. Chromatin and condensed chromosome structure
The deoxyribonucleic acid (or DNA) is considered the blueprint of life. A gene is a segment of the DNA that serves as a unit of heredity.
In eukaryotes, the genetic material is all stored within the nucleus bound by the nuclear membrane. In prokaryotes, the genetic material is suspended in the cytoplasm known as the nucleoid region.
The DNA wrapped in histones is termed as the chromosomes. The chromatid is one version of the duplicated chromosome. The chromatin is just the uncondensed counterpart of chromosomes. A genotype is a set of genes that influence and control the expression of
biological traits. A phenotypes is an observable trait expressed in an individual. A gene has four major units: exons, introns, promoter region, and enhancer
region.
A. Arrange the following levels of organization in the genetic materials within
organisms. Write your answer inside the stacked Venn below.
B. Match the following parts of a gene with their respective function. 1. Enhancer region a. coding region of the gene
2. Promoter region b. non-coding region of the gene 3. Introns c. regulates the activation of a gene 4. Extrons d. interacts to the transcription factor
5. Gene e. controls phenotypes
phosphate group
sugar group
4.
9.
Read the following questions carefully. Then, answer briefly.
With his work on the pea plant, an Austrian monk, Gregor Mendel, discovered the basic principles of inheritance. He spent a lot of his time crossing pea plants and noticed some patterns of inheritance of traits coming from one generation to the next. With his experiments, he was able to establish concepts known today as the laws of heredity. What are these laws of heredity?
Who Am I? Through this activity you will get to know yourself better through your classmates eyes. Materials:
bond paper pen clear tape
Procedure:
1. Using clear tape, place a whole sheet of paper on your back. (You may ask your classmates to help you with this.)
2. Try to scan the faces and physical attributes of your classmates. 3. On the papers placed on your classmates’ backs, write a specific physical
attribute for each of them. (Remember you are not allowed to give hurtful remarks.)
5. Remove the papers from your backs after the activity. 6. Compare the answers on your paper with a seatmate and make conclusions
per pair by answering the following questions below: Guide Questions:
1. Looking at your papers, were there traits that are similar? What are those? Infer some reasons as to why it is possible.
2. What are the traits that are different? List them down. What do you think contributes to your differences?
3. How can these similarities and differences benefit us?
with the terms below so that so you could understand the experiment very well.
Parental generation (P generation) – the initial generation. First filial generation (F1 generation) – the first set of offsprings from parent
generation. The F1 generation can reproduce to make the F2 generation and so on.
Pure-bred plants - these refer to plants that “always” produce an offspring with identical trait as the parent for many generations. For example, a parent plant with a tall trait crossed by a plant with the same trait will produce a 100% offspring with the tall trait.
Self-fertilization – some plants can fertilize by themselves. It is possible because some plants such as pea plants possess both reproductive organs (stamen and pistil)
Mendel did the pea plant experiment by first crossing two pure-bred plants. In Fig. 7., the purebred purple flower is crossed by a purebred white flower.
Fig. 8. The process on how Mendel did the pea plant experiment
two flowers using a paintbrush. He planted the seeds from the resulting matured pod. If the blending theory of inheritance is correct, the offspring should be a pea plant with a color in between the purple and white since the trait is mixed. However, the result of Mendel’s experiment after the cross, also called the F1 generation, is a 100% purple flower. As a result, this experiment disproved the former blending theory of inheritance. The resulting plants in the F1 generation were allowed to self-fertilize. If the blending theory of inheritance is correct, the result should be 100% purple flowers since the parent is just one which is the purple flower. However, the result is 75% purple and 25% white flower. This result is another proof that the blending theory of inheritance is incorrect.
Fig. 9. Result of the pea plant experiment
A dominant trait exists when a dominant allele masks the expression of the recessive allele, if present. Dominant alleles are often denoted by two uppercase letters or one uppercase, one lowercase letter. For example, tall is dominant for the height trait. Therefore, it is represented by TT or Tt.
A recessive trait exists if the dominant allele is not present. This trait has a pair of recessive alleles. It is written in small letters. For example, short is dominant for the height trait. Therefore, it is represented by tt.
In his pea plant experiment, Mendel found out the following dominant and recessive traits of pea plants.
The law of dominance states that a pure line (homozygous) dominant trait crossed with a recessive trait will result in the expression of the dominant trait for all the resulting offsprings. It is shown in the F1 generation of Mendel’s pea plant experiment. Purebred tall crossed by short pea plant result to the expression of the dominant trait which is tall in all the resulting offsprings.
Table 1. Pairing of alleles for genes controlling certain traits.
Genotype symbol Genotype classification Phenotype*
TT homozygous dominant tall
Tt heterozygous dominant tall
tt homozygous recessive short
* assuming that “t” is the gene that controls the height phenotype
Fig. 11. Resulting genes in each gametes after meiosis.
During sex cell formation, two alleles that code for a certain trait separate from one another to form sex cells that contain only one gene of the pair. During fertilization, the offspring tend to get one genetic allele from each parent, the egg and the sperm cells. The cell with the combined alleles from both parents now forms the offspring.
Law of Independent Assortment With Mendel’s work on several cross breeds of pea plants, he observed that the height of the plant (T), color (Y) and shape (R) of the seeds did not affect the inheritance of one another. A plant which is tall does not automatically mean that the plant will have yellow pods, nor did yellow seeds to have round shape. Mendel derived a conclusion that the different traits are inherited independently. The law of independent assortment explains that genes responsible for the expression of different traits are sorted independently from each other. This means that the inheritance of each trait is highly independent of the inheritance of other traits.
Fig. 13. Independent inheritance of pod shape (round = R; wrinkled = r) and
Color (yellow = Y; green = y) in pea plants.
Fig. 13 shows that different genes controlling for different traits such as pod shape and pod color are distributed in each gamete independently. One trait does not affect the inheritance of the other.
The three laws of Mendel explain how meiosis works. If you have a deep understanding on meiosis, the laws of Mendel are not a problem to you. Fig. 14. summarizes the three laws using the meiosis model.
Fig. 14. Meiosis and the laws of Mendel
A Punnett square is a graphical representation for predicting all possible resulting genotype combination of a specific cross or breeding experiment. To predict the resulting genotype combination, follow the steps below. Step 1 Draw a Punnett square by setting up a grid of perpendicular lines. Step 2 Place the genotype of one parent on the top. Step 3 Place the genotype of the other parent down the left side. Step 4 Fill the spaces at the center by copying the letters on the row and
column headings across or down into the empty squares.
Example 1 One dog is heterozygous for black haired trait (Bb), and its partner is homozygous white-haired trait (bb). Using the Punnett square, determine the ratio for the phenotype of their offspring. Solution Step 1 Identify the genotype both parents.
heterozygous black-haired traits × homozygous white-haired traits Bb × bb
Step 2 Construct the Punnett square for the cross.
2 Bb = Heterozygous black-haired trait 2 bb = Homozygous white-haired trait
Let us Practice Mendel crossed red flowered pea plants with white flowered pea plants. (Red flowers are dominant to white.) Both stocks of plants were homozygous. What color flowers will the offspring plants have?
Example 2 A red and a white flower were crossed and it resulted to a 0% probability for a white color flower. Red is dominant over white. Using the Punnett square, determine the possible phenotype of parents.
Solution
Step 1 Identify the genotype of the offspring. There are two genotype RR and Rr will result to red.
Step 3 Interpret the result.
Example 3 Two individuals who are carriers of the recessive allele for cystic fibrosis were crossed. Determine the probability of the offspring to inherit the said disease. Solution Step 1 Identify the genotype of both parents. Both of them are carrier of a recessive disease. Therefore, their genotype is heterozygous for the expression of cystic fibrosis.
Step 3: Interpret the result. 25% chance of having the cystic fibrosis (cc) 50% chance of to be a carrier of the disease (Cc) 25% chance of being healthy and not carrier of the recessive allele (CC)
Therefore, 25% of their offspring can inherit cystic fibrosis.
Mendel proposed three laws of heredity: the law of dominance, the law of
segregation, and the law of independent assortment. An allele controls similar traits but exhibits different phenotypes. A Punnett square is a graphical representation for predicting all possible
resulting genotype combination of a specific cross or breeding experiment.
For further information, you can check the following links:
A. Identify which Mendelian principle is being described below. Use A-law of
dominance, B-law of segregation, and C-law of independent assortment. 1. It states that the recessive trait is being masked. 2. Two alleles that code for a certain trait separate from one another during
sex cell formation. 3. The cell with the combined alleles from both parents forms the offspring. 4. There is a stronger gene in heterozygous pairing. 5. The inheritance of each trait is highly independent on the inheritance of
other traits. 6. The height of the plant (T), color (Y) and shape (R) of the seeds had no
effect on the inheritance of one another. 7. Alleles must segregate somewhere between the production of sex cells
and fertilization. 8. When there is a dominant homozygous gene, the resulting offspring will
only exhibit the dominant trait. 9. In the process of fertilization, the offspring tend to get one genetic allele
from each parent when the egg cell and the sperm cell unite. 10. Mendel derived a conclusion that the different traits are inherited
independently. B. Determine the resulting offspring and the percentage of the genotype based on the parents’ alleles.
Trait Parents’ Alleles Resulting Offspring
Percentage of the Genotype
Widow’s Peak E (widow’s peak) e (without widow’s peak)
EE × ee
Ll × ll
DD × dd
Hh × Hh
Read the following questions carefully. Then, answer briefly.
1. What are the differences among the Mendelian principles? 2. How do these principles help in the study of genetics? 3. Why did Mendel choose pea plants for his experiment on inheritance? 4. Green seed color is dominant over yellow. If you conducted a cross between
homozygous yellow plants (gg) and heterozygous green plants (Gg), what are the resulting genotypic and phenotypic ratios of the offspring?
pen and paper Procedure:
1. Find a partner. 2. Observe the flowers shown. List down your observations on a piece of
paper. 3. After 2 to 3 minutes, exchange papers with your partner and identify the
similar answers from your observations. Guide Questions:
1. What are your observations from the three pictures below ? 2. What are the possible reasons for your observation? Identify their
advantages.
Shown below is a cross through a Punnett square that exhibits the equal chances of having a female and a male offspring.
X Y
When the trait is linked to the X chromosome, it is called X-linked trait while if the trait is linked to the Y chromosome, it is called Y-linked trait. The x-linked trait is most common in males than females. It is because the males only have one X chromosome. Therefore, if a trait is linked to their single X chromosome, they will already exhibit it in their phenotype. In the case of females, it is less common since females have two X chromosome. It means that before the female express the X-linked trait, the trait should be linked in both X chromosomes. If only one of the chromosome is affected, the female is just a carrier of the trait but does not possess it in their phenotype. As a whole, the X-linked trait is more common in males because they have 1/2 or 50% chance for them to express the trait while females only have 1/3 or 33.3% chance of acquiring the trait. Table 2. Possible color blindness genotypes and phenotypes of males and females.
Female Male
XCX Carrier female XCY Colorblind male
XCXC Colorblind female
An example of a recessive x-linked trait in humans is hemophilia and colorblindness. Hemophilia is a genetic disorder that disallows the body to make blood clots. Hence, bleeding will not stop. On the other hand, color blindness is a trait wherein a person cannot distinguish colors properly. Both traits are found on the X chromosome, not on the Y. Table 2 shows the possible color blindness genotypes and phenotypes of males and females. Same genotypes could be used if dealing with the hemophilia trait. Just change the letter ‘C’ to ‘H’ to avoid confusion. The Y-linked trait is only common in males since only males have Y chromosome. Therefore, if the father possessed the Y-linked trait, all the male offsprings will acquire the trait. The female offspring will never acquire the trait. An example is the hypertrichosis pinnae auris trait. This trait is characterized by having a hairy ear. Sex-Influenced Trait Sex-influenced trait is an autosomal trait. As opposed to sex-linked trait, sex-influenced trait is not located on the sex chromosomes. However, the sex of a person influences the trait. It means that sex-influenced trait can be found in both sexes but expressed more in one sex than the other. An example of this is the baldness trait. Baldness is more common in males than females because they have 2/3 or 66.7 % chance of acquiring the trait. As shown in Table 3, the possibility of a male to acquire the trait is 2 (XBYB and XBXb) out of 3 genotypes. On the other hand, females only have 1/3 or 33.3 % chance of acquiring the trait. It is because the possibility of a female to acquire the trait is 1 (XBXB) out of 3 genotypes. Table 3. Possible baldness genotypes and phenotypes of males and females
Female Male
XBXB Bald XBYB Bald
XBXb Non-bald (normal) XBYb Bald
XbXb Non-bald (normal) XbYb Non-bald (normal)
Sex-Limited Trait Sex-limited trait is also an autosomal trait. Similar to sex-influenced trait, the sex of a person has something to do with the expression of the trait. It means that sex-limited traits could be found in both sexes but only one sex expresses it on their phenotype. An example of this trait is the lactation trait. This trait is both
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found in males and females. However, only the females express it on their phenotype. Table 4 shows that the trait is found in male genotypes but any genotype could not express the lactation trait in the phenotype of males. Table 4. Possible Lactation Genotypes and Phenotypes of Males and Females
Female Male
Genotypes Phenotypes Genotypes Phenotypes
XLXl Lactating XLYl Not lactating
XLXl Lactating XLYl Not lactating
XlXl Not lactating XlYl Not lactating
Multiple Alleles In some traits, a certain gene can have more than a pair of alleles that controls the expression of traits. This is evident in the patterns of inheritance in human blood type. The ABO blood type has three alleles (A, B, and O) governing this characteristic.
Table 5. Blood types and their corresponding genotypes
Blood Type Genotype
As shown in Table 5, genetic inheritance of blood type works in this manner:
Both the A and B are dominant alleles over O. Blood type O can be expressed by homozygous recessive, OO. Blood type A can have a homozygous dominant AA or heterozygous
dominant AO
Blood type B can have homozygous dominant BB or heterozygous dominant BO.
Blood type AB has codominant AB alleles because both are expressed equally in the phenotype of the individual with heterozygous gene.
Fig. 18. Multiple alleles controlling human blood type inheritance.
Example 1 Cross two pink snapdragons. Using the Punnett square, determine the percentage for the pink genotypic and phenotypic traits.
Solution Step 1 Identify the genotype of both parents.
heterozygous pink × heterozygous pink Rr × Rr
Step 3 Interpret the results.
2 Rr = Heterozygous pink snapdragons 1 rr = Homozygous white snapdragons 1 RR = Homozygous red snapdragons
The percentage for pink phenotype and genotype is both 50%.
Let us Practice What is the result of a cross between a pink snapdragon and a white snapdragon? Follow the same concept above.
Example 2 A woman who is a carrier of colorblindness trait marries a man who is colorblind (a recessive sex-linked trait). What are the chances of them having a son or daughter who is colorblind? Using the Punnett square, determine the probability of the offspring that is colorblind. Express your answer in percentage. Solution Step 1 Identify the genotype both parents.
Heterozygous normal vision × Homozygous colorblind XC X × XCY
Step 2: Construct the Punnett square for the cross.
X XC X XY
Step 3: Interpret the result.
1 XC XC = color blind daughter 1 XC X = carrier of colorblindness trait daughter 1 XC Y= color blind son 1 XY = son with normal vision
There is a 50% probability that the offspring will be colorblind.
Let us Practice Both parents have normal color vision. They had a daughter with normal vision and a son who is colorblind. What is the probability that the daughter is a carrier for the color-blindness allele?
Example 3 Mr. Anderson has straight hair while Mrs. Anderson has wavy hair. (The curly hair gene shows incomplete dominance. There are two alleles, curly- dominant and straight- recessive. The heterozygote has wavy hair.) The Andersons have a child with curly hair. Mr. Anderson accuses Mrs. Anderson of being unfaithful to him. Is he necessarily justified? Why or why not? Show your Punnett square and the corresponding solutions. Solution Step 1 Identify the genotype of both parents. Remember that Mr. Anderson has straight hair and Mrs Anderson has wavy hair.
Step 3 Interpret the result.
Mr. Anderson’s justification could justified since they have 0% chance of having a child with curly hair.
A non-Mendelian inheritance is a complex pattern of inheritance that does not follow the laws of heredity by Gregor Mendel.
Incomplete dominance is a pattern of inheritance characterized by the formation of a trait that is in between the phenotypes of the parents.
Codominance is a non-Mendelian type of dominance where the alleles of a gene pair in a heterozygote are fully expressed.
Genes that go along with either sex chromosome is said to be sex-linked.
For further information, you can check the following links:
A. Identify the phenotypes of the given genotypes.
10. XY __________________________________________________
B. Compute for the possible blood type of child based from the given data below.
Family name
Possible blood type of the child
Read the following questions carefully. Then, answer briefly. 1. How did the concept of non-Mendelian genetics come about? 2. What type of inheritance results in long radishes crossed with round
radishes results in all oval radishes? Explain your answer. 3. Hemophilia is a recessive sex-linked trait associated with the X
chromosomes in humans. If an unaffected male and carrier female were crossed, what is the probability of their children inheriting the disease?
4. A woman has a daughter and she claims that one of the three men is the biological father of her child. A paternity judge in the court requested that the woman, the daughter, and all three men have their blood types identified. The results are mother, Heterozygous Type A; Daughter, Type O; Man #1, Type AB; Man #2, Homozygous Type B; Man #3, Type O based on the blood types. The mother affirms that the results confirm that Man #3 is her daughter's father. Is she right? Why or why not?
Not all traits are governed by a single gene. Most of the time, the control in the expression of a single trait is affected by multiple genes. These genes may have a single or multiple pairs of alleles responsible for the high variation in the phenotype. How does multiple gene inheritance work?
Around and Around Materials:
color wheel Procedure:
1. Create a color wheel. Make a circle and divide it into four parts. Use the colors red, blue, yellow and green for each part. Fasten one arrow to a metal brad and place at the center of the circle.
2. Record the color for each time the wheel stopped.
1 2 3 4 5 6 7 8 9 10
Color
A monogenic inheritance involves only one gene and gives two possible
Compare polygenic traits to other non-mendelian inheritance traits by watching this video.
User: Amoeba Sisters. 2015. ‘Incomplete dominance, codominance, polygenic traits, and epistasis.’ https://www.youtube.com/watch?v=YJHGfbW55l0
Wondering how polygenic traits work? Click on this link. User: Great Pacific Media. 2009. ‘Polygenic Inheritance.’ https://www.youtube.com/watch?v=gouqTq5p168
A. Put a check on the traits that are considered under polygenic inheritance. 1. dimples 2. fur color 3. flower color 4. seed shape 5. weight 6. height 7. hemophilia 8. eye color 9. spots on animals
10. behavior B. Analyze the given statements below. Write MGI for monogenic inheritance, PGI
8. Genes are inherited independently from each other. 9. The inheritance that greatly contributes to very high variation among
Read the following questions carefully. Then, answer briefly.
1. Genes undergo a series of processes to be utilized in controlling the expression of traits among individuals. Is it possible for living organisms to have the same genes?
2. How do genes located on a single chromosome affect heredity? 3. Is eye color controlled by a single gene? Explain your answer. 4. Two different foster parents adopted a monozygotic identical twins at birth.
One child raised by a wealthy family in Canada while a low-income family adopted the other child in the Philippines. After 30 years, they met each other and observed differences in their phenotypes. What are the possible factors that have caused these differences in the identical twins?
Activity 2.1
Modelling Probability of Allele Inheritance Objectives At the end of this laboratory activity, the students should be able to:
determine how the parent’s alleles are segregated in the resulting gametes of the offsprings.
Materials and Equipment
2 small ziplock bags chocolate candies (2 red and 2 white)
Procedure
1. Put one red and one white chocolate candy on the first bag. The red candy represents a dominant allele while the white represents recessive allele. Label the bag as "mother's allele".
Table 1. F1 Generation.
Draw Allele from Mom Allele from Dad F1 Genotype F1 Phenotype
1
2
Class Total
Guide Questions
1. What does each bean represent? 2. What trait is being studied in this experiment? 3. Which genotype and phenotype would most likely be expressed by the
offspring of F1 generation.
Tracing the Cause of Genetic Disorder Goal
You are tasked to do a case study for a family who would wish to trace one genetic disorder.
Role
You are a geneticist in a hospital who specializes with family heredity. Audience
Your audience include the students and teachers from your school. Situation
You were assigned to work on case study of a family who would wish to determine their family’s genetic disorder. You are to assess the prevailing problem of the disorder and find solution/s to the stated dilemma. It will also require a survey questionnaire for the family’s interview. The case study should consider one genetic disease. The proposed study should be feasible and supported by scientific research. The final paper should be compiled in a long folder and should follow the guidelines for an academic paper.
Product, Performance, and Purpose:
Standards and Criteria: Your performance will be graded based on the rubric below.
Criteria Below
Exemplary 100%
Content Contents are related to the tasks
Less than 49% of the required components of assigned contents were presented in the case study.
50% - 70% of the the required components of assigned contents were presented in the case study.
75% - 90%of the required components of assigned contents were presented in the case study.
100%.of the required components of assigned contents were presented in the case study.
Organization Detailed facts are presented completely and in a cohesive flow.
Details shown in the plan were few and not cohesive throughout the submitted paper.
Details shown in the plan were few and began to show cohesiveness throughout the submitted paper.
Details shown in the plan were mostly complete and showed cohesiveness throughout the submitted paper.
Details shown in the plan were completed, provided additional details, and shows cohesiveness throughout the submitted paper.
Quality The paper has complete components and is neatly presented.
The product had incomplete components and relationships are inaccurately represented.
The product had components and relationships represented.
The product was neat, components and relationships are well represented.
The product was neat, components and relationships are accurately detailed and clearly represented.
Integrating concepts in Genetics Subject matter is integrated and properly used in presenting facts.
No concept of Genetics is not discussed in the tasks.
Reflect on your understanding of the topic by completing the sentences below.
Reflect
Chromatin This is a thread-like structure made up of DNA.
Chromosome It is a condensed structure that came about due to the coiling of chromatin structures.
Codominance This is a form of dominance wherein the gene pair is expressed simultaneously in an individual.
Deoxyribonucleic acid (DNA)
This is a long chain of nucleotide comprising of a phosphate group, a sugar group and nitrogenous bases (adenine, thymine, guanine and cytosine).
Dominant trait It is an allele that masks recessive traits. This is represented by a capital letter.
Enhancer region This is the one that interacts with the transcription factor to help the promoter region becomes activated
Exons These are coding regions of a gene.
Gene This is a unit of heredity that contains DNA segments.
Genotype These are set of genes that influences the expression of traits (phenotype)
Hemophilia It is a recessive genetic disorder that disables blood clot to occur.
Heterozygous It is also called as hybrids. This comprises of one dominant and one recessive allele.
Homozygous This set of allele is composed of both dominant or both recessive traits.
Incomplete dominance
It is a pattern of inheritance where the dominant alleles are not fully expressed and traits are blended.
Introns These are non-coding regions of a gene.
Law of dominance It is a mendelian principle that states that dominant traits will always masks the recessive traits.
Law of independent assortment
This states that traits are independently inherited from one another.
Law of segregation It is a law that states that alleles are segregated during gamete formation and fertilization.
Monogenic inheritance
It is a pattern of inheritance that involves only one gene.
Multiple gene inheritance
This is also called as polygenic inheritance. It is a trait of an individual controlled by more than one gene.
Multiple allele These are genes that have more than a pair of allele that controls the expression of traits.
Phenotype This is the observable traits which are controlled by genotype.
Promoter region It is a the regulatory sequences that regulate the activation of genes, which determine when and where the protein should be synthesized.
Punnett square This is a graphical representation used for predicting possible genotype and phenotypes.
Johnson, G.B., and Raven, P.H. 2001. Biology: Principles & Explorations. Austin:
Holt, Rinehart and Winston. Klug, W.S., Spencer, C.A., and Cummings, M.R. 2016. Concepts of Genetics. Boston:
Pearson. Mader, S.S. 2014. Concepts of Biology. New York: McGraw-Hill Education. Reece, J.B. and Campbell, N.A. 2011. Campbell Biology. Boston: Benjamin
Cummings/Pearson.
Tamarin, R.H. 2004. Principles of Genetics. Boston: McGraw-Hill. "Facts About Genetics: Chromosome18". 2018. Chromosome18.Org.
https://www.chromosome18.org/facts-about-genetics/.
Table of Contents
Objectives
Warm-Up
Lesson 2.1: Genes 5
Objectives Warm-up Learn about It Key Points Web Links Check Your Understanding Challenge Yourself
5 5 6
Lesson 2.2: Laws of Heredity and the Punnett Square 14
Objectives Warm-up Learn about It Key Points Web Links Check Your Understanding Challenge Yourself
14 14 15 27 27 28 29
Lesson 2.3: Non-Mendelian Inheritance 30
Objectives Warm-up Learn about It Key Points Web Links Check Your Understanding Challenge Yourself
30 30 31 40 40 40 42
Lesson 2.4: Multiple Genes 43
Objectives Warm-up Learn about It Key Points Web Links Check Your Understanding Challenge Yourself
43 43 44 46 46 46 47
Laboratory Activity 48
Performance Task 50
Self Check 52
Key Words 52
Wrap up 54
At the end of this unit, you should be able to answer the following questions. How are genes related to heredity? Why are genes important to human beings and other living organisms? How can the structure of genes affect the amino acid sequences? How were the pea plants used to generate the Mendelian laws? How are Punnett squares used to solve genetic problems? How did non-Mendelian patterns of inheritance occur? How are Mendelian laws different from non-Mendelian inheritance? Why is the environment a significant factor for traits considered under
multiple genes?
The deoxyribonucleic acid (or DNA) is the molecule responsible for carrying the genetic blueprint for the general identity of living organisms.
During meiosis, DNA is replicated, and the recombination between pairs of homologous chromosomes happen. Meiosis allows the exchange of genetic materials between chromosomes, leading to variations in the genetic makeup of the resulting haploid daughter cells. These haploid daughter cells are the gametes or sex cells.
Have you ever observed yourself in a mirror and wondered why you are the way you are? Or maybe, you have been fascinated at times, at how you are almost a carbon copy of your father, your mother, or a relative? Most of the times, people will tell you that you have the same traits as your parents because they passed their genes to you. What are genes, why are they important, and how do they affect you?
The Folk Hunt In this activity, you will roam around the room and guess whose parents are indicated in the picture. Materials:
picture of parents notebook
Procedure:
1. Have tables in a circle formation. 2. Take note of the letter that is assigned to you by your teacher. 3. Make sure to keep the photos of your parents hidden from your classmates
and indicate your assigned letter.
4. Randomly put the picture of your parents in different tables. 5. For five minutes, you will roam around the room and guess whose parents
are placed on the tables. Remember to indicate the letter for each picture that you are guessing.
Guide Questions:
1. How were you able to identify the parents of your classmates without meeting them?
2. What are the things that you have considered to accomplish the activity?
The gene consists of a specific nucleotide sequence and has a definite position in a given chromosome. This particular sequence codes for a specific protein for phenotype expression. A gene has four major units.
Exons are the coding regions, which are translated to a specific sequence of amino acids
Introns are the non-coding regions, which do not specify any amino acid sequence for protein synthesis.
The promoter region is the regulatory sequence that regulates the activation of genes, which also determines when and where the protein should be synthesized. The CAT and TATA boxes are components that are found in the promoter region.
Fig. 4. Chromosomes, DNA, and genes
Do not confuse chromosome with chromatin and chromatid. The chromosome is just the condensed version of chromatin. It means that chromatin is only evident during prophase while chromosome is evident during metaphase. The one that you can see in the microscope is chromosome, not chromatin. On the other hand, the chromatid is one version of the duplicated chromosome. Since there are 46 chromosomes in humans, the number of chromatids is 92. To help you remember the difference, bear in mind that a chromosome is also the same as sister chromatids.
Fig. 5. Difference of chromatin, chromatid, and chromosome.
Fig. 6. Chromatin and condensed chromosome structure
The deoxyribonucleic acid (or DNA) is considered the blueprint of life. A gene is a segment of the DNA that serves as a unit of heredity.
In eukaryotes, the genetic material is all stored within the nucleus bound by the nuclear membrane. In prokaryotes, the genetic material is suspended in the cytoplasm known as the nucleoid region.
The DNA wrapped in histones is termed as the chromosomes. The chromatid is one version of the duplicated chromosome. The chromatin is just the uncondensed counterpart of chromosomes. A genotype is a set of genes that influence and control the expression of
biological traits. A phenotypes is an observable trait expressed in an individual. A gene has four major units: exons, introns, promoter region, and enhancer
region.
A. Arrange the following levels of organization in the genetic materials within
organisms. Write your answer inside the stacked Venn below.
B. Match the following parts of a gene with their respective function. 1. Enhancer region a. coding region of the gene
2. Promoter region b. non-coding region of the gene 3. Introns c. regulates the activation of a gene 4. Extrons d. interacts to the transcription factor
5. Gene e. controls phenotypes
phosphate group
sugar group
4.
9.
Read the following questions carefully. Then, answer briefly.
With his work on the pea plant, an Austrian monk, Gregor Mendel, discovered the basic principles of inheritance. He spent a lot of his time crossing pea plants and noticed some patterns of inheritance of traits coming from one generation to the next. With his experiments, he was able to establish concepts known today as the laws of heredity. What are these laws of heredity?
Who Am I? Through this activity you will get to know yourself better through your classmates eyes. Materials:
bond paper pen clear tape
Procedure:
1. Using clear tape, place a whole sheet of paper on your back. (You may ask your classmates to help you with this.)
2. Try to scan the faces and physical attributes of your classmates. 3. On the papers placed on your classmates’ backs, write a specific physical
attribute for each of them. (Remember you are not allowed to give hurtful remarks.)
5. Remove the papers from your backs after the activity. 6. Compare the answers on your paper with a seatmate and make conclusions
per pair by answering the following questions below: Guide Questions:
1. Looking at your papers, were there traits that are similar? What are those? Infer some reasons as to why it is possible.
2. What are the traits that are different? List them down. What do you think contributes to your differences?
3. How can these similarities and differences benefit us?
with the terms below so that so you could understand the experiment very well.
Parental generation (P generation) – the initial generation. First filial generation (F1 generation) – the first set of offsprings from parent
generation. The F1 generation can reproduce to make the F2 generation and so on.
Pure-bred plants - these refer to plants that “always” produce an offspring with identical trait as the parent for many generations. For example, a parent plant with a tall trait crossed by a plant with the same trait will produce a 100% offspring with the tall trait.
Self-fertilization – some plants can fertilize by themselves. It is possible because some plants such as pea plants possess both reproductive organs (stamen and pistil)
Mendel did the pea plant experiment by first crossing two pure-bred plants. In Fig. 7., the purebred purple flower is crossed by a purebred white flower.
Fig. 8. The process on how Mendel did the pea plant experiment
two flowers using a paintbrush. He planted the seeds from the resulting matured pod. If the blending theory of inheritance is correct, the offspring should be a pea plant with a color in between the purple and white since the trait is mixed. However, the result of Mendel’s experiment after the cross, also called the F1 generation, is a 100% purple flower. As a result, this experiment disproved the former blending theory of inheritance. The resulting plants in the F1 generation were allowed to self-fertilize. If the blending theory of inheritance is correct, the result should be 100% purple flowers since the parent is just one which is the purple flower. However, the result is 75% purple and 25% white flower. This result is another proof that the blending theory of inheritance is incorrect.
Fig. 9. Result of the pea plant experiment
A dominant trait exists when a dominant allele masks the expression of the recessive allele, if present. Dominant alleles are often denoted by two uppercase letters or one uppercase, one lowercase letter. For example, tall is dominant for the height trait. Therefore, it is represented by TT or Tt.
A recessive trait exists if the dominant allele is not present. This trait has a pair of recessive alleles. It is written in small letters. For example, short is dominant for the height trait. Therefore, it is represented by tt.
In his pea plant experiment, Mendel found out the following dominant and recessive traits of pea plants.
The law of dominance states that a pure line (homozygous) dominant trait crossed with a recessive trait will result in the expression of the dominant trait for all the resulting offsprings. It is shown in the F1 generation of Mendel’s pea plant experiment. Purebred tall crossed by short pea plant result to the expression of the dominant trait which is tall in all the resulting offsprings.
Table 1. Pairing of alleles for genes controlling certain traits.
Genotype symbol Genotype classification Phenotype*
TT homozygous dominant tall
Tt heterozygous dominant tall
tt homozygous recessive short
* assuming that “t” is the gene that controls the height phenotype
Fig. 11. Resulting genes in each gametes after meiosis.
During sex cell formation, two alleles that code for a certain trait separate from one another to form sex cells that contain only one gene of the pair. During fertilization, the offspring tend to get one genetic allele from each parent, the egg and the sperm cells. The cell with the combined alleles from both parents now forms the offspring.
Law of Independent Assortment With Mendel’s work on several cross breeds of pea plants, he observed that the height of the plant (T), color (Y) and shape (R) of the seeds did not affect the inheritance of one another. A plant which is tall does not automatically mean that the plant will have yellow pods, nor did yellow seeds to have round shape. Mendel derived a conclusion that the different traits are inherited independently. The law of independent assortment explains that genes responsible for the expression of different traits are sorted independently from each other. This means that the inheritance of each trait is highly independent of the inheritance of other traits.
Fig. 13. Independent inheritance of pod shape (round = R; wrinkled = r) and
Color (yellow = Y; green = y) in pea plants.
Fig. 13 shows that different genes controlling for different traits such as pod shape and pod color are distributed in each gamete independently. One trait does not affect the inheritance of the other.
The three laws of Mendel explain how meiosis works. If you have a deep understanding on meiosis, the laws of Mendel are not a problem to you. Fig. 14. summarizes the three laws using the meiosis model.
Fig. 14. Meiosis and the laws of Mendel
A Punnett square is a graphical representation for predicting all possible resulting genotype combination of a specific cross or breeding experiment. To predict the resulting genotype combination, follow the steps below. Step 1 Draw a Punnett square by setting up a grid of perpendicular lines. Step 2 Place the genotype of one parent on the top. Step 3 Place the genotype of the other parent down the left side. Step 4 Fill the spaces at the center by copying the letters on the row and
column headings across or down into the empty squares.
Example 1 One dog is heterozygous for black haired trait (Bb), and its partner is homozygous white-haired trait (bb). Using the Punnett square, determine the ratio for the phenotype of their offspring. Solution Step 1 Identify the genotype both parents.
heterozygous black-haired traits × homozygous white-haired traits Bb × bb
Step 2 Construct the Punnett square for the cross.
2 Bb = Heterozygous black-haired trait 2 bb = Homozygous white-haired trait
Let us Practice Mendel crossed red flowered pea plants with white flowered pea plants. (Red flowers are dominant to white.) Both stocks of plants were homozygous. What color flowers will the offspring plants have?
Example 2 A red and a white flower were crossed and it resulted to a 0% probability for a white color flower. Red is dominant over white. Using the Punnett square, determine the possible phenotype of parents.
Solution
Step 1 Identify the genotype of the offspring. There are two genotype RR and Rr will result to red.
Step 3 Interpret the result.
Example 3 Two individuals who are carriers of the recessive allele for cystic fibrosis were crossed. Determine the probability of the offspring to inherit the said disease. Solution Step 1 Identify the genotype of both parents. Both of them are carrier of a recessive disease. Therefore, their genotype is heterozygous for the expression of cystic fibrosis.
Step 3: Interpret the result. 25% chance of having the cystic fibrosis (cc) 50% chance of to be a carrier of the disease (Cc) 25% chance of being healthy and not carrier of the recessive allele (CC)
Therefore, 25% of their offspring can inherit cystic fibrosis.
Mendel proposed three laws of heredity: the law of dominance, the law of
segregation, and the law of independent assortment. An allele controls similar traits but exhibits different phenotypes. A Punnett square is a graphical representation for predicting all possible
resulting genotype combination of a specific cross or breeding experiment.
For further information, you can check the following links:
A. Identify which Mendelian principle is being described below. Use A-law of
dominance, B-law of segregation, and C-law of independent assortment. 1. It states that the recessive trait is being masked. 2. Two alleles that code for a certain trait separate from one another during
sex cell formation. 3. The cell with the combined alleles from both parents forms the offspring. 4. There is a stronger gene in heterozygous pairing. 5. The inheritance of each trait is highly independent on the inheritance of
other traits. 6. The height of the plant (T), color (Y) and shape (R) of the seeds had no
effect on the inheritance of one another. 7. Alleles must segregate somewhere between the production of sex cells
and fertilization. 8. When there is a dominant homozygous gene, the resulting offspring will
only exhibit the dominant trait. 9. In the process of fertilization, the offspring tend to get one genetic allele
from each parent when the egg cell and the sperm cell unite. 10. Mendel derived a conclusion that the different traits are inherited
independently. B. Determine the resulting offspring and the percentage of the genotype based on the parents’ alleles.
Trait Parents’ Alleles Resulting Offspring
Percentage of the Genotype
Widow’s Peak E (widow’s peak) e (without widow’s peak)
EE × ee
Ll × ll
DD × dd
Hh × Hh
Read the following questions carefully. Then, answer briefly.
1. What are the differences among the Mendelian principles? 2. How do these principles help in the study of genetics? 3. Why did Mendel choose pea plants for his experiment on inheritance? 4. Green seed color is dominant over yellow. If you conducted a cross between
homozygous yellow plants (gg) and heterozygous green plants (Gg), what are the resulting genotypic and phenotypic ratios of the offspring?
pen and paper Procedure:
1. Find a partner. 2. Observe the flowers shown. List down your observations on a piece of
paper. 3. After 2 to 3 minutes, exchange papers with your partner and identify the
similar answers from your observations. Guide Questions:
1. What are your observations from the three pictures below ? 2. What are the possible reasons for your observation? Identify their
advantages.
Shown below is a cross through a Punnett square that exhibits the equal chances of having a female and a male offspring.
X Y
When the trait is linked to the X chromosome, it is called X-linked trait while if the trait is linked to the Y chromosome, it is called Y-linked trait. The x-linked trait is most common in males than females. It is because the males only have one X chromosome. Therefore, if a trait is linked to their single X chromosome, they will already exhibit it in their phenotype. In the case of females, it is less common since females have two X chromosome. It means that before the female express the X-linked trait, the trait should be linked in both X chromosomes. If only one of the chromosome is affected, the female is just a carrier of the trait but does not possess it in their phenotype. As a whole, the X-linked trait is more common in males because they have 1/2 or 50% chance for them to express the trait while females only have 1/3 or 33.3% chance of acquiring the trait. Table 2. Possible color blindness genotypes and phenotypes of males and females.
Female Male
XCX Carrier female XCY Colorblind male
XCXC Colorblind female
An example of a recessive x-linked trait in humans is hemophilia and colorblindness. Hemophilia is a genetic disorder that disallows the body to make blood clots. Hence, bleeding will not stop. On the other hand, color blindness is a trait wherein a person cannot distinguish colors properly. Both traits are found on the X chromosome, not on the Y. Table 2 shows the possible color blindness genotypes and phenotypes of males and females. Same genotypes could be used if dealing with the hemophilia trait. Just change the letter ‘C’ to ‘H’ to avoid confusion. The Y-linked trait is only common in males since only males have Y chromosome. Therefore, if the father possessed the Y-linked trait, all the male offsprings will acquire the trait. The female offspring will never acquire the trait. An example is the hypertrichosis pinnae auris trait. This trait is characterized by having a hairy ear. Sex-Influenced Trait Sex-influenced trait is an autosomal trait. As opposed to sex-linked trait, sex-influenced trait is not located on the sex chromosomes. However, the sex of a person influences the trait. It means that sex-influenced trait can be found in both sexes but expressed more in one sex than the other. An example of this is the baldness trait. Baldness is more common in males than females because they have 2/3 or 66.7 % chance of acquiring the trait. As shown in Table 3, the possibility of a male to acquire the trait is 2 (XBYB and XBXb) out of 3 genotypes. On the other hand, females only have 1/3 or 33.3 % chance of acquiring the trait. It is because the possibility of a female to acquire the trait is 1 (XBXB) out of 3 genotypes. Table 3. Possible baldness genotypes and phenotypes of males and females
Female Male
XBXB Bald XBYB Bald
XBXb Non-bald (normal) XBYb Bald
XbXb Non-bald (normal) XbYb Non-bald (normal)
Sex-Limited Trait Sex-limited trait is also an autosomal trait. Similar to sex-influenced trait, the sex of a person has something to do with the expression of the trait. It means that sex-limited traits could be found in both sexes but only one sex expresses it on their phenotype. An example of this trait is the lactation trait. This trait is both
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found in males and females. However, only the females express it on their phenotype. Table 4 shows that the trait is found in male genotypes but any genotype could not express the lactation trait in the phenotype of males. Table 4. Possible Lactation Genotypes and Phenotypes of Males and Females
Female Male
Genotypes Phenotypes Genotypes Phenotypes
XLXl Lactating XLYl Not lactating
XLXl Lactating XLYl Not lactating
XlXl Not lactating XlYl Not lactating
Multiple Alleles In some traits, a certain gene can have more than a pair of alleles that controls the expression of traits. This is evident in the patterns of inheritance in human blood type. The ABO blood type has three alleles (A, B, and O) governing this characteristic.
Table 5. Blood types and their corresponding genotypes
Blood Type Genotype
As shown in Table 5, genetic inheritance of blood type works in this manner:
Both the A and B are dominant alleles over O. Blood type O can be expressed by homozygous recessive, OO. Blood type A can have a homozygous dominant AA or heterozygous
dominant AO
Blood type B can have homozygous dominant BB or heterozygous dominant BO.
Blood type AB has codominant AB alleles because both are expressed equally in the phenotype of the individual with heterozygous gene.
Fig. 18. Multiple alleles controlling human blood type inheritance.
Example 1 Cross two pink snapdragons. Using the Punnett square, determine the percentage for the pink genotypic and phenotypic traits.
Solution Step 1 Identify the genotype of both parents.
heterozygous pink × heterozygous pink Rr × Rr
Step 3 Interpret the results.
2 Rr = Heterozygous pink snapdragons 1 rr = Homozygous white snapdragons 1 RR = Homozygous red snapdragons
The percentage for pink phenotype and genotype is both 50%.
Let us Practice What is the result of a cross between a pink snapdragon and a white snapdragon? Follow the same concept above.
Example 2 A woman who is a carrier of colorblindness trait marries a man who is colorblind (a recessive sex-linked trait). What are the chances of them having a son or daughter who is colorblind? Using the Punnett square, determine the probability of the offspring that is colorblind. Express your answer in percentage. Solution Step 1 Identify the genotype both parents.
Heterozygous normal vision × Homozygous colorblind XC X × XCY
Step 2: Construct the Punnett square for the cross.
X XC X XY
Step 3: Interpret the result.
1 XC XC = color blind daughter 1 XC X = carrier of colorblindness trait daughter 1 XC Y= color blind son 1 XY = son with normal vision
There is a 50% probability that the offspring will be colorblind.
Let us Practice Both parents have normal color vision. They had a daughter with normal vision and a son who is colorblind. What is the probability that the daughter is a carrier for the color-blindness allele?
Example 3 Mr. Anderson has straight hair while Mrs. Anderson has wavy hair. (The curly hair gene shows incomplete dominance. There are two alleles, curly- dominant and straight- recessive. The heterozygote has wavy hair.) The Andersons have a child with curly hair. Mr. Anderson accuses Mrs. Anderson of being unfaithful to him. Is he necessarily justified? Why or why not? Show your Punnett square and the corresponding solutions. Solution Step 1 Identify the genotype of both parents. Remember that Mr. Anderson has straight hair and Mrs Anderson has wavy hair.
Step 3 Interpret the result.
Mr. Anderson’s justification could justified since they have 0% chance of having a child with curly hair.
A non-Mendelian inheritance is a complex pattern of inheritance that does not follow the laws of heredity by Gregor Mendel.
Incomplete dominance is a pattern of inheritance characterized by the formation of a trait that is in between the phenotypes of the parents.
Codominance is a non-Mendelian type of dominance where the alleles of a gene pair in a heterozygote are fully expressed.
Genes that go along with either sex chromosome is said to be sex-linked.
For further information, you can check the following links:
A. Identify the phenotypes of the given genotypes.
10. XY __________________________________________________
B. Compute for the possible blood type of child based from the given data below.
Family name
Possible blood type of the child
Read the following questions carefully. Then, answer briefly. 1. How did the concept of non-Mendelian genetics come about? 2. What type of inheritance results in long radishes crossed with round
radishes results in all oval radishes? Explain your answer. 3. Hemophilia is a recessive sex-linked trait associated with the X
chromosomes in humans. If an unaffected male and carrier female were crossed, what is the probability of their children inheriting the disease?
4. A woman has a daughter and she claims that one of the three men is the biological father of her child. A paternity judge in the court requested that the woman, the daughter, and all three men have their blood types identified. The results are mother, Heterozygous Type A; Daughter, Type O; Man #1, Type AB; Man #2, Homozygous Type B; Man #3, Type O based on the blood types. The mother affirms that the results confirm that Man #3 is her daughter's father. Is she right? Why or why not?
Not all traits are governed by a single gene. Most of the time, the control in the expression of a single trait is affected by multiple genes. These genes may have a single or multiple pairs of alleles responsible for the high variation in the phenotype. How does multiple gene inheritance work?
Around and Around Materials:
color wheel Procedure:
1. Create a color wheel. Make a circle and divide it into four parts. Use the colors red, blue, yellow and green for each part. Fasten one arrow to a metal brad and place at the center of the circle.
2. Record the color for each time the wheel stopped.
1 2 3 4 5 6 7 8 9 10
Color
A monogenic inheritance involves only one gene and gives two possible
Compare polygenic traits to other non-mendelian inheritance traits by watching this video.
User: Amoeba Sisters. 2015. ‘Incomplete dominance, codominance, polygenic traits, and epistasis.’ https://www.youtube.com/watch?v=YJHGfbW55l0
Wondering how polygenic traits work? Click on this link. User: Great Pacific Media. 2009. ‘Polygenic Inheritance.’ https://www.youtube.com/watch?v=gouqTq5p168
A. Put a check on the traits that are considered under polygenic inheritance. 1. dimples 2. fur color 3. flower color 4. seed shape 5. weight 6. height 7. hemophilia 8. eye color 9. spots on animals
10. behavior B. Analyze the given statements below. Write MGI for monogenic inheritance, PGI
8. Genes are inherited independently from each other. 9. The inheritance that greatly contributes to very high variation among
Read the following questions carefully. Then, answer briefly.
1. Genes undergo a series of processes to be utilized in controlling the expression of traits among individuals. Is it possible for living organisms to have the same genes?
2. How do genes located on a single chromosome affect heredity? 3. Is eye color controlled by a single gene? Explain your answer. 4. Two different foster parents adopted a monozygotic identical twins at birth.
One child raised by a wealthy family in Canada while a low-income family adopted the other child in the Philippines. After 30 years, they met each other and observed differences in their phenotypes. What are the possible factors that have caused these differences in the identical twins?
Activity 2.1
Modelling Probability of Allele Inheritance Objectives At the end of this laboratory activity, the students should be able to:
determine how the parent’s alleles are segregated in the resulting gametes of the offsprings.
Materials and Equipment
2 small ziplock bags chocolate candies (2 red and 2 white)
Procedure
1. Put one red and one white chocolate candy on the first bag. The red candy represents a dominant allele while the white represents recessive allele. Label the bag as "mother's allele".
Table 1. F1 Generation.
Draw Allele from Mom Allele from Dad F1 Genotype F1 Phenotype
1
2
Class Total
Guide Questions
1. What does each bean represent? 2. What trait is being studied in this experiment? 3. Which genotype and phenotype would most likely be expressed by the
offspring of F1 generation.
Tracing the Cause of Genetic Disorder Goal
You are tasked to do a case study for a family who would wish to trace one genetic disorder.
Role
You are a geneticist in a hospital who specializes with family heredity. Audience
Your audience include the students and teachers from your school. Situation
You were assigned to work on case study of a family who would wish to determine their family’s genetic disorder. You are to assess the prevailing problem of the disorder and find solution/s to the stated dilemma. It will also require a survey questionnaire for the family’s interview. The case study should consider one genetic disease. The proposed study should be feasible and supported by scientific research. The final paper should be compiled in a long folder and should follow the guidelines for an academic paper.
Product, Performance, and Purpose:
Standards and Criteria: Your performance will be graded based on the rubric below.
Criteria Below
Exemplary 100%
Content Contents are related to the tasks
Less than 49% of the required components of assigned contents were presented in the case study.
50% - 70% of the the required components of assigned contents were presented in the case study.
75% - 90%of the required components of assigned contents were presented in the case study.
100%.of the required components of assigned contents were presented in the case study.
Organization Detailed facts are presented completely and in a cohesive flow.
Details shown in the plan were few and not cohesive throughout the submitted paper.
Details shown in the plan were few and began to show cohesiveness throughout the submitted paper.
Details shown in the plan were mostly complete and showed cohesiveness throughout the submitted paper.
Details shown in the plan were completed, provided additional details, and shows cohesiveness throughout the submitted paper.
Quality The paper has complete components and is neatly presented.
The product had incomplete components and relationships are inaccurately represented.
The product had components and relationships represented.
The product was neat, components and relationships are well represented.
The product was neat, components and relationships are accurately detailed and clearly represented.
Integrating concepts in Genetics Subject matter is integrated and properly used in presenting facts.
No concept of Genetics is not discussed in the tasks.
Reflect on your understanding of the topic by completing the sentences below.
Reflect
Chromatin This is a thread-like structure made up of DNA.
Chromosome It is a condensed structure that came about due to the coiling of chromatin structures.
Codominance This is a form of dominance wherein the gene pair is expressed simultaneously in an individual.
Deoxyribonucleic acid (DNA)
This is a long chain of nucleotide comprising of a phosphate group, a sugar group and nitrogenous bases (adenine, thymine, guanine and cytosine).
Dominant trait It is an allele that masks recessive traits. This is represented by a capital letter.
Enhancer region This is the one that interacts with the transcription factor to help the promoter region becomes activated
Exons These are coding regions of a gene.
Gene This is a unit of heredity that contains DNA segments.
Genotype These are set of genes that influences the expression of traits (phenotype)
Hemophilia It is a recessive genetic disorder that disables blood clot to occur.
Heterozygous It is also called as hybrids. This comprises of one dominant and one recessive allele.
Homozygous This set of allele is composed of both dominant or both recessive traits.
Incomplete dominance
It is a pattern of inheritance where the dominant alleles are not fully expressed and traits are blended.
Introns These are non-coding regions of a gene.
Law of dominance It is a mendelian principle that states that dominant traits will always masks the recessive traits.
Law of independent assortment
This states that traits are independently inherited from one another.
Law of segregation It is a law that states that alleles are segregated during gamete formation and fertilization.
Monogenic inheritance
It is a pattern of inheritance that involves only one gene.
Multiple gene inheritance
This is also called as polygenic inheritance. It is a trait of an individual controlled by more than one gene.
Multiple allele These are genes that have more than a pair of allele that controls the expression of traits.
Phenotype This is the observable traits which are controlled by genotype.
Promoter region It is a the regulatory sequences that regulate the activation of genes, which determine when and where the protein should be synthesized.
Punnett square This is a graphical representation used for predicting possible genotype and phenotypes.
Johnson, G.B., and Raven, P.H. 2001. Biology: Principles & Explorations. Austin:
Holt, Rinehart and Winston. Klug, W.S., Spencer, C.A., and Cummings, M.R. 2016. Concepts of Genetics. Boston:
Pearson. Mader, S.S. 2014. Concepts of Biology. New York: McGraw-Hill Education. Reece, J.B. and Campbell, N.A. 2011. Campbell Biology. Boston: Benjamin
Cummings/Pearson.
Tamarin, R.H. 2004. Principles of Genetics. Boston: McGraw-Hill. "Facts About Genetics: Chromosome18". 2018. Chromosome18.Org.
https://www.chromosome18.org/facts-about-genetics/.
Table of Contents
Objectives
Warm-Up