Big Idea 16: Heredity and Reproduction

Description   A. Reproduction is characteristic of living things and is essential for the survival of species. B. Genetic information is passed from generation to generation by DNA; DNA controls the traits of an organism. C. Changes in the DNA of an organism can cause changes in traits, and manipulation of DNA in organisms has led to genetically modified organisms.

Benchmark Number & Descriptor

• SC.7.L.16.1• Understand and explain that every organism requires a set of

instructions that specifies its traits, that this hereditary information (DNA) contains genes located in the chromosomes of each cell, and that heredity is the passage of these instructions from one generation to another.

• SC.7.L.16.2• Determine the probabilities for genotype and phenotype combinations

using Punnett Squares and pedigrees.• SC.7.L.16.3• Compare and contrast the general processes of sexual reproduction

requiring meiosis and asexual reproduction requiring mitosis.• SC.7.L.16.4• Recognize and explore the impact of biotechnology (cloning, genetic

engineering, artificial selection) on the individual, society and the environment.

WHO ARE YOU?

DNA• DNA =

Deoxyribonucleic Acid• Traits which are

passed from parents to offspring are carried in DNA.

• DNA is a blueprint for the cells in an organism.

• Without DNA, an organisms traits would never form.

DIRECTIONSGENES

• Pieces of DNA• Carry traits

• Characteristics

• Help pass traits from parent to offspring– You inherit your genes.

• Offspring receive only some genes from parents.

• Genes combine differently, so you look different.

CHROMOSOMES• Genes are located on

chromosomes.– Thousands of genes can be

found on a single chromosome.

• Chromosomes are found in the nucleus of the cells.

• Each type of organism contains a set number of chromosomes.– Humans = 23 Pairs

PUTTING IT ALL TOGETHER

KNOWLEDGE CHECK

1. What does DNA stand for?

2. Where is DNA located?

3. Why is DNA important?

KNOWLEDGE CHECK

1. What does DNA stand for? Deoxyribonucleic Acid

2. Where is DNA located? DNA is located on genes which are carried by chromosomes.

3. Why is DNA important? It’s the blueprint for how organisms are made.

WHY DON’T WE LOOK ALIKE?

What is Heredity?• Heredity is the passing on

of characteristics (traits) from parents to offspring.

• Genetics is the study of heredity.

Gregor Mendel

• WHO: – Austrian monk

• WHAT: – Worked with pea plants and discovered how traits get

passed from generation to generation

• WHEN: – Around 1856

PASSING OF TRAITS• Each gene contains 2 ALLELES

– 1 allele from mom– 1 allele from dad

• Individual alleles are represented by an upper or lowercase letter.

• Some alleles are dominant, and others are recessive.

BLUE = alleleRED = allele

together = gene

TRAITSTYPES OF TRAITS

• The trait that is observed in the offspring is the DOMINANT TRAIT (uppercase).– It only takes one dominant allele for that

trait to be shown.

• The trait that disappears in the offspring is the RECESSIVE TRAIT (lowercase).– It takes 2 recessive alleles for that trait to

be shown.

LETTER COMBINATIONS

• Heterozygous - if the two alleles for a trait are different (Aa)– Also referred to as a hybrid

combination

• Homozygous - if the two alleles for a trait are the same (AA or aa)– Also referred to as a

purebred combination

TRAITSGENOTYPE

• Refers to the letter (allele) combination– TT, Tt. tt

• If a capital letter is present in the letter pair, the dominant trait will be expressed in that organism.

• If 2 lower case letters are paired, the recessive trait will be expressed in that organism.

PHENOTYPE• Refers to the physical

characteristic being expressed

• Uses words/phrases to describe not letters

• Examples: – tall, short– white, black

PUNNETT SQUARES • Tool used to determine

characteristics of offspring• Each box represents the

probability of an offspring receiving a trait.– Example:

• Top outside (Tt) is a gene passed on by the father

• Left outside (tt) is a gene passed on by the mother.

• 4 middle boxes are possible gene combinations an offspring may receive.

T

t

T

t

Tt

Tt

Tt

Tt

T = Tallt = ShortAll offsprings will be tall (all boxes contain the dominant trait for tallness).

PUNNETT SQUARES• Short hair (L) is

dominant to long hair (l) in mice. What is the genotype and phenotype ratio of a heterozygous short-haired mouse crossed with a long-haired mouse?

• Punnett Square: L l

l l

• Genotype ratio: ½ Ll: ½ ll

• Phenotype ratio: ½ short hair: ½ long hair

Ll ll

Ll ll

PEDIGREE• A chart used to trace

traits throughout a family

• Parts of the chart– Circle = females– Squares = males– Half-filled in/Dotted =

carrier• Have the gene but do

not show signs of it– Filled-in = affected

• Have both the gene and symptoms of that trait

KNOWLEDGE CHECK

1. What do we call the trait that is observed?

2. What case (upper or lower) is it written in?

3. What about the one that disappears?

4. What case is it written in?

• Trait Tall = Aa • Trait short = aa• Aa x aa5. Complete the Punnett Square.

____ ____

____

____

KNOWLEDGE CHECK1. What do we call the

trait that is observed? Dominant

2. What case (upper or lower) is it written in? Upper

3. What about the one that disappears? Recessive

4. What case is it written in? Lower

• Trait Tall = Aa • Trait short = aa• Aa x aa5. Complete the Punnett

Square.

__A_ __a_

_a__ Aa aa

_a__ Aa aa

HOW DO WE GET ALL THIS STUFF?

REPRODUCTIONSEXUAL

• Primary method of reproduction for the vast majority of visible organisms, including almost all animals and plants

• Characterized by two processes:– meiosis, halving of the

number of chromosomes– fertilization, combination of

two gametes and the restoration of the original number of chromosomes

• Results in increasing genetic diversity of the offspring.

ASEXUAL• A form of reproduction

which does not involve meiosis or fertilization

• Asexual reproduction = one parent.

• The primary form of reproduction for single-celled organisms such as archaea, bacteria, and protists

• Mitosis is the main way of reproduction.

REPRODUCTIONASEXUAL

• MITOSIS– All forms of asexual

reproduction utilize the process of mitosis.

– Begins with one replication (copying of the chromosome material) and one division of the chromosome material  

– This results is 2 daughter cells being produced with the same number of and identical chromosomes as in the parent cell.

Asexual reproduction in liverworts: a caducuous phylloid germinating

Mitosis• Interphase

– Normal functions– Upon trigger,

chromosomes & centrioles duplicate.

• Prophase– Early: nuclear envelope

degrades; chromosomes start to condense.

– Late: chromosomes thicken; spindle forms between centrioles

• Metaphase– Spindle fibers attach to

kinetochores.– Chromosomes line up at

cell equator.

sdst.org/shs/apbio/... /mitosis powerpoint.ppt

Mitosis• Anaphase

– Chromatids separate at centromeres

– Chromosomes move to poles.

• Telophase– Nuclear envelope

reforms in each of two daughter cells.

– Cytokinesis separates two new cells.

• Interphase– Daughter cells are

genetically identical to each other and the parent cell but smaller.

sdst.org/shs/apbio/... /mitosis powerpoint.ppt

REPRODUCTIONSEXUAL

• MEIOSIS– Process produces the sex

cells• Contain ½ the chromosomes

as the parent

– Since ½ male chromosomes and ½ female chromosomes combine = genetic variety

Hoverflies mating in midair flight.

MEIOSIS • Prophase I: the chromosomes

condense and homologous chromosomes pair up to form tetrads.

• Metaphase I: the tetrads are all arranged at the metaphase plate.

• Anaphase I: the homologous chromosomes separate and are pulled toward opposite poles.

• Telophase I: movement of homologous chromosomes continues until there is a haploid set at each pole.

• Cytokinesis : by the same mechanisms as mitosis usually occurs simultaneously

• Prophase 2: spindle reforms and chromosomes move toward the metaphase plate.

• Metaphase 2: sister chromatids lined up on themetaphase plate.

• Anaphase 2: sister chromatids are separated and pulled toward opposite poles of the cell.

• Telophase 2 and Cytokinesis: nuclei form ateither pole, and each cell is finally divided into two identical daughter cells.

MEIOSIS

Mitosis vs. Meiosis

REPRODUCTIONSEXUAL

• EXAMPLES: – Sexual Reproduction

• DNA from 2 individuals merge to form one.

• Animals, plants

– Fertilization• Pollen is delivered to female

part of plant.• Flowering plants

ASEXUAL• EXAMPLES:

– Fragmentation/Regeneration• Body of parent breaks and

produces offspring.• Fungi, moss, sea stars,

planarian

– Budding• Offspring grows out of parent.• Yeast, hydras

KNOWLEDGE CHECK1. Label each of the following as either Asexual or

Sexual reproduction: • Spores budding• Nearly all organisms reproduce this way• Mitosis• Meiosis• Starfish is cut in half; both halves grow into a

whole starfish.• One parent needed• Not identical to parents• Two parents needed• Identical to parent• Sperm and eggs

KNOWLEDGE CHECKASEXUAL SEXUAL

• Spores budding• Mitosis• Starfish is cut in half; both

halves grow into a whole starfish.

• Identical to parent• One parent needed

• Not identical to parents• Two parents needed• Sperm and eggs• Meiosis• Nearly all organisms

reproduce this way.

SHOULD WE MESS WITH MOTHER

NATURE?

MAKING IT JUST RIGHTSELECTIVE BREEDING

• The process of using specific plants or animals with specific traits to reproduce offspring with those traits

• These breeded plants/animals can be: – Larger in size– Provide more food– Resistant to disease

HYBRIDIZATION• The process of crossing to

plants/animals with different variations of the same trait

• The resulting offspring is created to have the best traits of the parents.

• Examples: – Corn: farmers each year try to

grow corn that are disease free and higher quality.

– Animals: if 2 different species are bred, a stronger but sterile species may be produced

MAKING IT JUST RIGHT

• Involves using two plants/animals that have the same or similar genes.

• The offspring produced will be purebred.• If purebreds are created, specific genes can be passed along.• Inbreeding, though, can cause a population to die.

– Since they are genetically similar, if one animal/plant comes down with a disease, the entire population may have it.

• INBREEDING

BREEDING EXAMPLES

Due to inbreeding, all cheetahs are closely related.

Miniature Horse was specifically bred small to work in mines.

Disease resistance, greater nutritional value

Mule combines the best traits of a horse and a donkey.

GENETIC ENGINEERING• Processes in which genes with specific DNA

strands are removed and transferred into another organism. – This process is much faster then altering organisms

through breeding techniques.

• Genetic engineering is used in biotechnology, medicine, and cloning.

GENETIC ENGINEERINGBIOTECHNOLOGY

• Involves growing cells for industrial purposes

• Agriculture: – Many plants and crops are

susceptible to disease.– Scientists have been able to

isolate fighting genes and insert them into plants/crops for better survival rates.

GENETIC MODIFICATION• Genetic engineering produces

a lot of strong feelings among people.

• PROS: – Crops and farm animals may be

produced to better tolerate drought, disease, and infestations, therefore increasing the food production around the world.

• CONS: – Many people are concerned

about mixing genetic material with different species.

– Once in the wild, the effects of changes are out of the scientists hands.

GENETIC ENGINEERINGMEDICINES

• Insulin has been able to be created through Genetic engineering.– Insulin was once made from

animals, but people were allergic to it. Now it is created from bacteria with no allergies and is less expensive.

• Vaccines have been able to be produced through Genetic engineering.– Vaccines such as Hepatitis B are

now less expensive to produce and can be made in mass production.

CLONING• Clones are living things that

have exactly the same genes.

• Agriculture has done this forever: – Taking clippings of plants and

replanting them– The cuttings grow into new

and identical plants.• Humans and animals,

however, become more controversial:– Is it ok to clone spare body

parts?

GENETIC ENGINEERINGGENE THERAPY

• Faulty genes inside a human bodies can be replaced with normal, healthy ones

• Unfortunately, most cells in our body only live for a short period of time. – The new cells with the new

genes can function for a short period of time.

WHAT WOULD YOU DO?

• The more we know about DNA and genes, the more we may be able to predict our future.

• People today can be screened for certain genetic conditions.

• For example – If a person is found to be a

carrier of a specific gene defect, he/she will need to make a choice if he/she are to have kids.

– Perhaps you carry a gene for cancer which may or may not turn on. What would you do?

KNOWLEDGE CHECK1. Name three types of breeding and a

reason why they are used.

2. What is Genetic engineering?

3. Why is Genetic engineering supported by some yet forbidden by others?

KNOWLEDGE CHECK1. Name three types of breeding and a reason why they are

used. Selective breeding, hybridization, inbreeding. All 3 can be used to make specific higher yielding crops. Crops less vulnerable to disease and animals for specified jobs

2. What is Genetic engineering? Processes in which genes with specific DNA strands are removed and transferred into another organism.

3. Why is Genetic engineering supported by some yet forbidden by others? Supported = create medicines and cells for people to survive

Forbidden = Messing with mother nature. Do not have control if changes were to get into the wild