Genetics

Chapter 10.2, 10.3, 11.1, and 11.2

Do Now- True for False if false, correct the statement. 1. Certain acquired characteristics, such as

mechanical or mathematical skill may be inherited. 2. Certain thoughts or experiences of a mother

mark or alter the hereditary makeup of an unborn child.

3. Color blindness is more common in males than in females.

4. A person may transmit characteristics to offspring which he/she does not show.

5. Certain inherited traits may be altered by the stars, planets or moon early in development.

6. The total number of male births exceeds female births each year.

Objectives 1. SWBAT hypothesize about the birth of

two twin boys. 2. SWBAT define homozygous,

heterozygous, gene, allele, and cross pollination

3. SWBAT discuss Mendel’s life and the importance of his study of pea plants.

The Problem…. Born October of 2006: These two boys are related… They are

twins. http://www.msnbc.msn.com/id/15447465/

Another Example…

How Can this be? Let’s Brainstorm.

Goal of this chapter on Genetics:

1866 Gregor Mendel “Father of Genetics” Austrian Monk that studied pea plants

Pure breeds Self Fertilization

Statistician who wanted to be a teacher

Discovered how traits were inherited in a population

How Genetics Began The passing of traits to the next

generation - inheritance or heredity.

Mendel performed cross-pollination in pea plants.

Mendel followed various traits in the pea plants he bred.

7 Traits Mendel Studied

Mendel studied seven different traits.

Seed or pea color Flower color Seed pod color Seed shape or texture Seed pod shape Stem length Flower position

Mendel’s Crosses P Generation:

F1 Generation:

F2 Generation:

Generations P Generation

Parents Pure –

F1 Generation Hybrid – 2 different types of genes for a trait

F2 Generation 3:1–Yellow : Green

Animation

Definitions Genetics:

Study of hereditary Gene:

Strand of DNA that codes for a protein (Trait) Allele:

A version of a gene

Phenotype vs. Genotype Phenotype:

Physical characteristics (What the individual looks like)

Ex) Red Petals

Genotype: Alleles Received (genes you have) Ex) RR

Homozygous and Heterozygous Homozygous:

Having two of the same alleles for a particular trait

Ex.

Heterozygous: Having two different alleles for a particular

trait Ex.

Dominant Vs. Recessive Dominant hides the recessive trait in the

heterozygous genotype.

Think – Pair - Share If Fred Flintstone is heterozygous for black hair. (B=Black, b=blonde)

What is Fred’s genotype?

What is Fred’s phenotype?

Tweety bird is yy. (Y= yellow feathers, y=brown feathers) 1. What is his genotype?

2. What is his phenotype?

3. Is he heterozygous or homozygous? Explain.

Objectives 1. SWBAT do a probability lab in which

they flip a coin to determine the outcome of crosses.

2. SWBAT will work in partners to create punnett squares.

Do Now Provide an example of the following

terms: Heterozygous Homozygous Genotype Phenotype Dominant Recessive Allele Gene

Mendels 3 Laws 1. Law of Segregation

Each allele a person has separates into different gametes

Ex. Ww – one W goes in one sperm and the other w goes into another sperm

w W

w W

Sperm

Mendels 3 Laws 2. Law of

Independent Assortment Gene pairs

(homologous) will separate randomly into gametes

Mendels 3 Laws 3. Law of Dominance

Traits exist in two possible forms (dominant and recessive)

The dominant forms hides the recessive trait in the heterozygous condition

Monohybrid Cross R= Can roll your tongue r= Can’t roll your tongue

Genotype Ratio:

Phenotype Ratio:

R r

R

r

Genotypic vs. Phenotypic Ratios Phenotype Ratio:

Ratio of different physical traits Ex) Brown eyes ¼ or 25%

Genotype Ratio: Ratio of the different possible alleles Ex) Tt = ¼ or 25%

Sample Problems1) Daffy Duck is heterozygous for black

feathers. Daisy Duck is homozygous for yellow feathers. Set up a punnett square and determine probabilities of their potential offspring. (Both genotype and phenotype ratios!)

2) B = Black b = yellow

Do Now Sponge Bob Square pants is heterozygous

for brown eyes. Sandy is also heterozygous for brown eyes. Create a punnett square to determine the possible outcomes of their children.

Do Now Sleeping Beauty has freckles. Her prince

charming is heterozygous for no freckles. What are the chances of her children having freckles? Please show your work.

Setting up Dihybrid Crosses 1. Determine parent genotypes 2. Determine alleles to be passed down 3. Set up punnet square 4. Determine outcome

Phenotype Ratio Genotype Ratio

Dihybrid Crosses Looking at two different traits

Ex. Hair color and eye color

B=brown eyes b=blue eyes

R=Brown hair r=blonde hair

Mother is heterozygous for both traits Father is heterozygous for eye color and homozygous

dominant for hair color

The problem Aladdin and Jasmine want to have

children. Jasmine is homozygous dominant for black hair and black eyes.

Aladdin is homozygous recessive for brown eyes and brown hair.

B=black hair b=brown hairE=black eyes e=brown eyes

B=black hair b=brown hairE=black eyes e=brown eyes

Jasmine’s daughter falls in love with a man who is also heterozygous for hair and eye color. Determine possible genotype and phenotype ratios.

Do Now BbTt X BBTt

Math Method For a cross between TtBb and TtBB. Do each cross individually and multiply the

results together.

For TtBb

Do Now Mickey Mouse is heterozygous for Round ears

and homozygous for Black eyes. Minnie Mouse also is homozygous for Floppy ears and heterozygous for Black eyes. Determine genotype and phenotype ratios. (B=black, b=brown, R=round, r= floppy.)

Quiz next class on 10.2 QUIZ ON THURS ON:

Vocabulary words Mendel Mendel’s experiments Monohybrid crosses ONLY

Do Now Peter and Lois decide to try for a 4th child. Determine the possible genotype and

phenotype ratios of the following cross:

DdEe X ddEe

D= Brown hair d=red hair E=fluffy hair e=thinning hair

Do Now Two dogs have puppies! The male dog

is homozygous brown fur and heterozygous floppy ears. The female dog is heterozygous for brown fur and has straight ears.

B=brown fur b=blonde fur F=Floppy ears f= straight ears

What ratio of the dogs would have brown fur and floppy ears?

10.3 Gene Linkage and Polyploidy Several genes on a chromosome Gene Linkage:

When two genes are close to each other on the same chromosome

Gene Linkage Linked genes on a chromosome results in

an exception to Mendel’s law of independent assortment

Linked genes usually do not segregate independently

Drosophila (Fruit Flies) First organism with linked genes Linked genes typically travel together

during crossing over http://www.biologyreference.com/La-Ma/Li

nkage-and-Gene-Mapping.html

Chromosome Map Crossing over occurs more frequently

between genes that are far apart Map of genes on a chromosomes and

frequency of crossing over

Polyploidy Occurrence of one or more extra sets of all

chromosomes in an organism. Ex. A triploid organism (3n) - means that it

has three complete sets of chromosomes.

True or False – Correct false statements_______   1. Crossing over occurs more frequently

between genes that are close together on a chromosome.

_______   2. Gene linkage was first studied by using garden peas.

_______   3. Scientists call a drawing like the one shown below a chromosome map.

_______   4. Chromosome map percentages represent actual chromosome distances.

Matching

11.1 Basic Pattern of Human Inheritance

Recessive Genetic Disorders Cystic Fibrosis Albinism Tay Sachs Disease Galactosemia

Affects the mucus-producing glands, digestive enzymes, and sweat glands

Chloride ions are not absorbed into the cells of a person with cystic fibrosis but are excreted in the sweat.

Without sufficient chloride ions in the cells, a thick mucus is secreted.

Cystic Fibrosis

Cystic Fibrosis Not too long ago CF was always fatal in

childhood, but better treatment methods developed over the past 20 years have increased the average lifespan of CF patients to nearly 30 years

Albinism Caused by altered genes, resulting in the

absence of the skin pigment melanin in hair and eyes

White hair Very pale skin Blue Eyes Pink pupils

Albinism Impaired Vision It is vital that people with

albinism use sunscreen when exposed to sunlight to prevent premature skin aging or skin cancer

High risk of skin cancer

Tay-Sachs Disease Caused by the absence of

the enzymes (in lysosomes) responsible for breaking down fatty acids called gangliosides

Gangliosides accumulate in the brain, inflating brain nerve cells and causing mental deterioration

Tay Sachs Disease Children with Tay-Sachs, a progressive

neurodegenerative disease that attacks nerve cells, usually die before age 5.

Children will go deaf, have seizures, and, ultimately, become unable to swallow or breathe.

Galactosemia Recessive genetic disorder characterized

by the inability of the body to digest galactose.

Lactose = Galactose + Glucose Symptoms: • liver damage or failure

• cataracts• brain damage• infection

Galactosemia Treatment requires the strict exclusion of

lactose/galactose from the diet.

Do Now Period 3

Dominant Genetic Disorders Dominant Gene results in disorder:

Huntington’s Disease Achondroplasia

Achondroplasia is a genetic condition that

causes small body size and limbs that are comparatively short.

Obesity Breathing problems (apnea) Recurrent ear infections

(otitis media). Other health problems

Matching Do Now Period 8

Huntington’s Disease affects the nervous system. Huntington's disease is a progressive,

degenerative disease that causes certain nerve cells in your brain to waste away.

As a result, you may experience uncontrolled movements, emotional disturbances and mental deterioration.

Huntington’s Disease Diminished memory,

immediate and short-term (long-term memory usually remains intact)

Disease usually manifests itself by age 35

Do Now Peter and Lois decide to try for a 4th child. Determine the possible genotype and

phenotype ratios of the following cross:

DdEe X ddEe

D= Brown hair d=red hair E=fluffy hair e=thinning hair

Do Now Explain how gene distances are

determined on a chromosome.

What does “3n” mean?

Pedigree Shows history of a trait in a family Allows researchers to analyze traits within

a family

Symbols for Pedigree

Using Pedigrees Inferring Genotypes

Knowing physical traits can determine what genes an individual is most likely to have.

Predicting Disorders Scientists use pedigree analysis to study: inheritance patterns determine phenotypes genotypes.

Sample Pedigree

Think – Pair - Share

Do Now Fill in the pedigree for Achondroplasia. Use

the variable A.

Dominant or Recessive Trait?

Dominant or Recessive Trait?

Test Cross When the genotype of an individual is

unknown, cross the individual with a homozygous recessive

The outcome of the cross determine the genotype of the unknown

11.2 Incomplete Dominance: Heterozygous phenotype is an

intermediate phenotype between the two homozygous phenotypes.

Two alleles are blended Ex) Four O’clock Flowers Red + WhiteWhite = Pink

Codominance Neither trait is dominant instead, both

traits are shown (No Blending) Ex) Roan Cows Red + WhiteWhite = RED AND WHITE

Sickle Cell Disease Affects red blood cells and ability to

transport oxygen.

Homozygous recessive alleles=

Heterozygous=

Homozygous dominant alleles=

Sickle Cell and Malaria People who are

heterozygous for sickle cell, have a higher resistance to malaria.

Do Now Fill in the genotypes for the following

pedigree B=brown eyes b = blue eyes

Do Now Explain how gene distances are

determined on a chromosome.

What does “3n” mean?

Multiple Alleles Traits determined by

more than 2 allelesEx. Blood Typing (3 alleles ABO) A and B are dominant

to O

Universal Donor

Sample Problem Determine the possible offspring of the

following crosses

1. AB and O 2. AA and BO 3. AB and AB

Coat Color of Rabbits Rabbits have a hierarchy of coat color 4 alleles (C, cch, ch, and c) Dominant C > cch> ch > c Recessive

C Full color cch Chinchilla ch Himalayan c albino

Complex Inheritance and Human Heredity

Coat Color of Rabbits

Full Color Himalayan

Albino

Chinchilla

Do Now period 6 cc x Ccch

Genotype and phenotype ratios

Do Now A parent with the blood type A and one

with B have a child with type O blood. What are the parents genotypes?

Draw out the punnett square.

Do Now Do the following cross between the these

rabbits. Cch x Ccch

What color were the parents? What are the genotype and phenotype

ratios of the offspring.

What do you see?

What do you see?

Sex Linked Traits Traits located on the sex chromosomes

(X or Y) X linked: gene is located on the X

chromosomes Y linked: gene is located on the Y

chromosome

What are the chances of having a girl?

How would you go about solving it?

Sex-Linked Traits A man who is color blind marries a woman

that is heterozygous for color blindness. What is the chance of having a color blind boy?

Do Now- per. 1 A man that is color blind marries a woman

that is a carrier for the disorder. What is the chance of having a color blind girl?

Hemophilia Sex linked disorder characterized by

delayed blood clotting Located on the X Chromosome Seen in the Royal Family of England

Hemophilia

Do Now – A man with hemophilia marries a woman

the is homozygous normal phenotype. What is the chance of having a boy with hemophilia?

A girl with hemophilia?

Complex Inheritance and Human Heredity

Polygenic Traits

Polygenic traits arise from the interaction of multiple pairs of genes.

Chapter 11

Skin Pigment

Polygenic Inheritance

Figure 9.22

P Generation

aabbcc(very light)

AABBCC(very dark)

F1 Generation

AaBbCc AaBbCc

F2 Generation

Eggs Sperm

What is the difference between polygenetic and multiple alleles?

Complex Inheritance and Human Heredity

Environmental Influences

Environmental factors

Diet and exercise

Sunlight and water

Temperature

Complex Inheritance and Human Heredity

Twin Studies

Helps scientists separate genetic contributions from environmental contributions

Traits that appear frequently in identical twins are at least partially controlled by heredity.

Traits expressed differently in identical twins are strongly influenced by environment.

Let’s try to explain the inheritance of the babies’ skin color.