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Packet #12 – Mendelian Genetics Summer 2014

This Activity Packet belongs to:

_________________________

At the end of the unit you will turn in this packet. Record the completion due dates in the chart below.

You should expect a variety of quizzes: announced, unannounced, open-notes and closed-notes.

If this packet is LOST, please: drop it off at the BHS Science Dept. (rm 365) OR

drop it off in Ms. Brunson’s classroom (rm 351) OR

call the Science Dept. at (617) 713-5365.

Packet

page Activity

Points

Earned Available

Human Genetic Traits 5

Chances' Choices 14

Probability and Genetics (plus notes) 14

Notes: Patterns of Inheritance --- ---

Solving Genetics Problems 15

Mendelian Genetics Test Review 5

Total

What is Genetics?______________________________________

____________________________________________________

____________________________________________________

____________________________________________________

Human Genetic Traits

Introduction: It does not matter what animal or plant you examine, virtually no two individuals of a

species are exactly alike. Every individual of a species has variations; variations are the product of genes

being passed from parent to offspring. For example, pea plants can vary in the color of their seeds,

carnations vary in the color and size of their flowers, gorillas vary in the wrinkles on their nose, and bears

can vary in the thickness and length of their coats. These are, in no way, the only variations between

individuals of these species, they are one in ten, hundreds, or thousands of variations.

What is the source for the variations we observe between and within species? Life is intimately linked to

molecular interactions. Is there a molecule that is responsible for the biological variations that we can

observe? How is it possible that a single molecule could code for biological differences?

In this journal, you will have the opportunity to examine some of the many variations within a single

species... humans. Using the biology class as a sample population, you will identify a few of the many

variations. Upon completion of the activity, you will take a few selected traits to determine your genetic

number and find your biology class twin or triplet or maybe quadruplet.

Pre-activity questions: (Do NOT use a book. Instead, answer with what you THINK you know!)

1. What are genes made of?

2. What do genes do?

3. How much of your DNA came from your biological Mother? From your biological Father?

4. How much of your DNA do you share with siblings (if you have them)?

5. Name 2 variations you get from DNA and 2 variations that don’t come from DNA.

Procedure:

1. Your teacher will guide you through the list of traits. First, circle your version for the trait.

2. Next, compile the class frequency for each trait (in percentage).

Trait

Variation #1 Variation #2

Variation Class frequency

(%) Variation

Class frequency

(%)

Gender Male Female

Tongue Rolling Yes No

Cheek Dimples Yes No

Earlobe Ends Attached Free

Chin Cleft Yes No

Freckles Yes No

Hair color Dark Light

Widow’s Peak Yes No

Hair curl Straight Nonstraight

Eye Color Non-blue Blue

Color Vision Normal Color-blind

Finger Interlocking Right on top Left on top

Mid-digit finger hair Yes No

Hitchhiker’s thumb Yes No

PTC taster Yes No

Chances' Choices

1. How to read a pedigree:

= =

=

=

=

Paul and Stacy:

2. What is state-mandated testing of newborns? Give some examples of diseases tested for.

3. What is PKU? Below is a schematic of what happens in this disease. Describe the symptoms.

4. Describe dominant vs. recessive traits and genotypes.

5. Explain why it makes sense that PKU is recessive (at a molecular level).

6. Do Frank and Alan have the gene for this enzyme? _____

7. Do Frank and Alan carry the allele that causes PKU?

a. Let’s review meiosis (spermatogenesis in Paul):

Before After Metaphase I

Interphase Interphase

Prophase II Metaphase II

Sperm cells

b. What are Paul and Stacy’s genotypes? Remember – they each have TWO copies of this gene

________ x ________

c. Which alleles could be in Paul’s sperm? How many copies of this gene will go into the sperm?

____ or ____

d. Which alleles could be in Stacy’s eggs? How many copies of this gene will go into the egg?

____ or ____

e. Using a Punnett square to make predictions:

f. What fraction of Paul and Stacy’s children do we expect to have PKU? ________

g. What are the chances of Paul and Stacy having another child with PKU? ________

8. What does each row or column in a Punnett square represent? ___________________

9. What does each individual box represent? ____________________

P

p

Scene 2: Will Alan ever play for the Celtics?

10. What is an X-linked trait?

11. How do you show an X-linked trait in a genotype?

12. What is hemophilia?

13. What are the chances of Paul and Stacy have a child with hemophilia AND PKU?

Parent's genotypes: _________ x _________

Paul Stacy

Chromosomes in metaphase I of Meiosis:

Paul: Stacy:

OR OR

Gametes: ______, ______, ______, ______ ______, ______, ______, ______

Too complicated? Another way to do it using probability:

PKU: Hemophilia: Sex:

Multiply fractions to get overall probability!

So...

A. What are the chances of Paul and Stacy having a child with hemophilia AND PKU?

B. What are the odds of an individual child being a boy?

C. What are the chances of having a girl with hemophilia?

D. What are the chances of having a girl that is a carrier of hemophilia and a carrier of PKU?

Probability and Genetics

Introduction: If someone flips a coin, you know that there are two possible outcomes: heads or tails.

You can predict how likely either is to happen. Can you make similar predictions about the outcomes of

genetic events? In this activity, you will use biological data to explore the concept of probability.

Probability is a mathematical tool that enables us to make predictions. We will provide you with

information about the offspring of two rabbits, and you will look for patterns in the results. This activity

is an altered version of “Game of Chance” on page 420 of the BSCS textbook.

Pre-Journal Discussion:

Genes and alleles

Genotypes and Phenotypes

Heterozygous and Homozygous

Law of Dominance

Procedure: (2 pt)

1. When flipping a coin, what is the probability, in percent, that a single coin toss will result in

heads? In tails?

2. Why is a coin toss a good way to represent allele combinations that occur in nature?

Materials: one penny per student

Procedure:

1. Solve the following problems. (1 pt)

a. A pair of rabbits mated and produced 10 offspring. How many males and how many females

would you predict are in those offspring? (statistically – not a guess) (Fill into table below)

b. Even if you are reasonably confident that your prediction is correct, can you guarantee how

many males and females will be born in the litter? Explain your answer.

2. Test your prediction by using a coin to simulate the sex of the 10 offspring. (1 pt)

3. Look at the data below – these show the results of 3 rabbit matings. (2 pt)

Small sample size

Trial # of offspring Males Females

1

2

3

10

10

10

4

6

6

6

4

4

a. Do these results match your predictions or test results from step 1?

4. Next investigate the relationship between probable outcomes, actual results, and sample size.

Examine the data below. Note that the total number of offspring is 600. Calculate the percentage of

male rabbits for each group of 600 offspring. Record these results in the table. (Percentage males =

[(# males) / (# total offspring)] x 100)

Large sample size

Trial # of offspring # Males # Females % Males

1

2

3

600

600

600

279

296

316

321

304

284

5. Answer the following questions: (2 pt)

a. Are these results generally closer to 50 percent than those in the small sample size (step 3)?

b. Based on your observation, what effect does sample size have on the match between probable

outcomes and actual results?

Predicted Actual

Heads (girls)

Tails (boys)

Analysis and Discussion: (1 pt each)

1. Use what you have learned about the importance of sample size (number of trials) to evaluate the

following medical study reported in a local newspaper.

“A study reported in a medical journal Acta Artifacta appears to link ownership

of fast cars with premature balding. The study, consisting of 17 men who own

sports cars, found that nearly 70 percent suffered from premature balding. The

authors of the study conclude that because this percentage of balding is much

higher than in the general population, there is an increased chance of suffering

from premature baldness if one owns a fast car.”

2. If you flip a coin five times and get heads every time, what is the probability that you will get tails

on the next flip?

3. Restate the following accurately: One out of every two offspring that results from a cross between

parents with the Genotypes Hh and hh definitely will have Huntington’s disease. [Hint:

Huntington’s disease is a dominant trait]

4. Evaluate the following claims. Who is right? Explain.

Marcia – “I really think we should have another child. I know we already have 5 boys, but I’ve

always wanted a little girl. Since I’ve had 5 boys already, probability says that I am overdue for a

girl. I am much more likely to have a baby girl this time.”

Tom – “We have enough children already. Plus, you are no more likely to end up with a girl this

time than any other time. You could end up with 6 boys and then where would we be!?!”

Probability and Genetics Notes

What role does probability play in genetics?

Sample size?

Accuracy of predictions?

What does meiosis have to do with inheritance?

(Law of Segregation)

How is variation guaranteed in offspring?

a.

b.

c.

Why do we use Punnett Squares?

Types of Inheritance Notes

Simple Dominance

Incomplete Dominance (and an example)

Codominance (and an example)

Polygenic traits (and an example)

There are 3 alleles for blood type: ____, ____, ____.

The blood types (and their genotypes) are:

Type A blood: _______ or _______

Type B blood: _______ or _______

Type AB blood: _______

Type O blood: _______

Blood type is determined by which _______________ you have on your blood cells

If you are missing a certain antigen, the body develops ____________________ that attack that

antigen if they encounter it.

Type A blood has antibodies against _______ antigens

Type B blood has antibodies against _______ antigens

Type AB blood has antibodies against ______ antigens

Type O blood has antibodies against ______ antigens

Solving Genetics Problems

When doing genetics problems, you should always: write all answers (neatly) on a separate piece of

paper. Number the problems and show all work/ explain your reasoning.

Mendelian Genetics – you should know: Law of Segregation, Law of Dominance, Law of Independent

Assortment, dominant, recessive, homozygous, heterozygous, genotype, phenotype, how to set up symbols,

the meaning of a Punnett square, probability.

Rules of probability:

Rule of multiplication

Rule of addition – not used often in genetics

Show all of your work on a separate piece of paper. Remember to use a strategy when you solve problems:

i. Establish an __________________.

ii. Write the parental ________________.

iii. Figure out what _____________ each parent can make.

iv. Set-up a Punnett Square.

v. Answer the stated question(s).

Simple Dominance

1. Long eye-lashes are dominant over short eye-lashes. Cross a heterozygous long eye-lashed mother with a

homozygous long eye-lashed father. What is the chance that these parents will have a long eye-lashed

offspring?

2. Normal skin is dominant over albino (the absence of pigment). Cross an albino mother with a heterozygous

father. What is the chance that these parents will have an albino child? What is the chance that these parents

will have an albino son?

3. If two animals heterozygous for a single trait are mated and have 200 offspring, about how many offspring

would you predict to have the dominant phenotype?

4. A male and a female, each with free earlobes (a dominant trait), give birth to a daughter with attached earlobes

(a recessive trait).

a.) If the couple has three more children, what is the chance that ALL of them will also have attached

earlobes?

b.) If the couple then has one more child (the first three are already born), what is the chance that this child

will also have attached earlobes?

c.) What is the chance that this fourth child will be a BOY with attached earlobes?

Alternate forms of inheritance

5. Suppose that red and white show incomplete dominance in a certain kind of flower. You cross a red flower

with a white flower. What percentage of the offspring do you expect to be pink? If you were to cross two of

these pink flowers, what ratios of color would you expect to see in the next generation?

6. Incomplete dominance is seen in the inheritance of hypercholesterolemia. Mack and Toni are both

heterozygous for this characteristic, and both have elevated levels of cholesterol. They give birth to a daughter,

Zoe, with a cholesterol level 6x higher than a “normal level,” and Zoe can be assumed to be homozygous for

this trait. If Mack and Toni have one more child, what is the probability that the child will suffer from the more

serious form of hypercholesterolemia seen in Zoe? (CL = low cholesterol, CH = high cholesterol)

7. Redraw this pedigree and label the genotypes of everyone. If this couple has a fourth child, could it have blood

type B? Explain.

type A type B

type AB type A type O

8. Use the following table to answer the next question:

Phenotype/

Blood Type

Genotype Antibodies in the

blood

A

B

AB

O

IAIA or IAi

IBIB or IBi

IAIB

ii

Anti-B

Anti-A

None

Anti-A and Anti-B

What are the possible blood types of children born to the following couples? (You do not need to draw a

Punnett Square for each, but be careful to consider ALL possibilities!)

a.) type A female, type A male c.) type A female, type O male

b.) type B female, type AB male d.) type AB female, type AB male

Independent Assortment (Crosses with two or more traits)

Remember!

When dealing with 2 traits, a genotype has FOUR letters, representing 2 copies of each gene (example –

AaBb).

When a person makes a sperm or egg (gamete), they put one copy of EACH gene in the gamete. This

means the gamete would contain TWO letters (one of each).

You can set up a large 4x4 Punnett square (like we did with Chance’s Choices) or you can use multiple 2x2

Punnett squares and use the rules of probability.

9. In seeds, corn can be either yellow (Y) or purple (y). Seed texture can be either smooth (S) or wrinkled (s).

Suppose a heterozygous plant is crossed with a plant that is homozygous dominant for color and heterozygous

for texture. What percent of the offspring will be yellow and wrinkled?

10. Bill and Barbara both have freckles, and Barbara has a widow's peak while Bill has a straight hairline. They

give birth to a daughter, Sarah, has no freckles and a straight hairline. Freckles and a widow’s peak are both

dominant, whereas no freckles and no widow’s peak are both recessive.

a.) What is Bill's genotype? What is Barbara's genotype?

b.) What is the chance that they will give birth to a second child with freckles and a widow's peak?

c.) What is the chance that they will have a boy with freckles and a widow's peak?

11. In the animal called ipsywoodles,

B=black fur F=forked tongue H=hairy body N=normal wings L=long bristles

b=yellow fur f=plain tongue h=normal body n=straight wings l=short bristles

If you crossed a heterozygous black furred, plain tongued, homozygous hairy bodied, heterozygous normal

winged, heterozygous long bristled ipsywoodle (phew! – try saying that ten times fast!), with the same type of

ipsywoodle, how many of the offspring would have: (don’t even think about trying a large Punnett Square

here…use multiple smaller Punnett squares…)

a.) black fur, forked tongue, hairy body, normal wings, long bristles

b.) black fur, plain tongue, hairy body, normal wings, short bristles

c.) yellow fur, plain tongued, hairy body, straight wings, long bristles

X-Linked Traits (Like Hemophilia in Chances’ Choices)

12. Red-green color blindness is a sex-linked trait, carried on the X chromosome. Why are there more color-blind

men than color-blind women?

13. Hemophilia is a disease caused by a recessive gene on the X chromosome. In a family, there are the following

children: 2 hemophiliac boys, a normal boy, a hemophiliac girl, and a normal girl. Draw a pedigree for this

family. What must the genotypes of the parents be? What is the genotype of each child?

Pedigrees:

14. Using the pedigrees below, predict the genotypes for all family members. For pedigree A, assume the shaded

trait is dominant and for pedigree B, assume the shaded trait is recessive. (Remember that you cannot fill in the

genotype of a dominant individual unless you KNOW for sure what his/her genotype is - don't guess!) Write

the letters on the lines provided.

15. Draw a pedigree for a family showing two parents and four children as follows:

(a) make the 2 oldest children boys and the two youngest girls.

(b) label the marriage line and the children line

(c) label the individuals and the generations with numbers

(d) Indicate person II-2 has attached earlobes (a recessive trait)

(e) Fill in the genotypes and symbols to indicate the remaining family’s traits

Vocabulary

Genotype

Phenotype

Allele

Dominant

Recessive

Homozygote

Heterozygote

Autosome

Sex chromosomes

Crossing over

Homologous

Chromosomes

Quest Outline for Mendelian Genetics

1. What is the relationship between sample size and accuracy of prediction?

2. Explain the different causes of variation, including when they occur (mutations, independent

assortment, crossing over, random fertilization).

3. Define each of Mendel’s Laws (Law of Dominance, Law of Independent Assortment, Law of

Segregation) and give a concrete example of each.

4. Be able to solve genetics problems, including:

a. 1 trait Punnett squares (2x2)

b. 2 or more trait Punnett squares using probability

c. Incomplete dominance & co-dominance

d. Blood typing

5. What is the relationship between meiosis, fertilization, and chance of

inheritance?

6. What is crossing over and when does it occur?

7. What is the relationship between genetics and environment?

8. What patterns would you see in a pedigree for a trait that is:

a. Autosomal Dominant?

b. Autosomal Recessive?

c. Sex-linked Recessive?

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