Finishing Up Mendelian Genetics

AIM: How can our genes affect our health and how can the environment affect our genes?

DO NOW: Handout

HOMEWORK: Review sheet

TEST ON TUESDAY, 2/15/11

Do Now

1. Which of the following crosses can never produce a child with blood type O?

a) O x AB b) A x B c) A x O d) O x O

Do Now

2. In squirrels, the gene for gray fur (G) is dominant over the gene for black fur (g). If 50% of a large litter of squirrels are

gray, the parental cross that produced this litter was most likely

a) GG x Gg b) GG x GG c) Gg x gg d) gg x gg

3. Some individuals with blood group A may inherit the genes for blond hair, while other individuals with blood

group A may inherit the genes for brown hair. This can be explained by the principle of

a) dominance b) multiple alleles c) independent assortment d) incomplete dominance

Do Now

What’s another way to say “two recessive traits”?

A. If mom or dad is heterozygous for a recessive genetic disorder, would they be normal or sick? What would their kid be?

Carriers – a parent that is heterozygous for a recessive genetic disorder

I. Genetic Disorders

B. If mom or dad is heterozygous for a dominant genetic disorder, would they be normal or sick? Could their kid be sick?

Huntington’s Disease

1. Huntington’s disease affects the nervous system and causes a gradual loss of brain function, uncontrollable movements, and emotional disturbances. There is no cure.

Stop and think! Are there any carriers in dominant genetic

disorders?

II. Sex-Linked Traits

What genotype makes an organism male?

What genotype makes an organism female?

XY

XX

A. Men only get one X chromosome. If there happens to be a recessive gene on the X, men don’t have a dominant gene that can cancel it out. They are going to express it.

B. Females have a far greater chance of having a dominant gene to hide the recessive one.

C. Sex-linked traits – traits carried by either the X or the Y chromosome

D. Sex-linked trait example: Color Blindness

Color blindness is a gene located on theX-chromosome.

Who would be more likely to be affected by this gene? Men or women?

E. Sex-linked trait example: Hemophilia

1. Hemophilia – characterized by really slow clotting of the blood

III. Polygenic Traits

A. Most traits are the result of the action of many genes (One trait = many genes).

ex. Skin color, hair color, and height depend upon the interaction of many independent genes.

B. Polygenic traits are controlled by two or more genes.1. They show a wide range of phenotypes

III. Environmental Influences on Heredity

Your genes are not the final answer!

A. There is so much that can be influenced by the environment, including nutrition, exercise, and where you live.

B. Genes + Environment = PhenotypeEx. Diseases like diabetes or

ulcers may be in a genetic code, but may never be

seen in the phenotype if the person leads a healthy

lifestyle.

Analyze the phrase, “Heredity loads the gun, but environment pulls

the trigger”

SUMMARY

How can our genes affect our health? Give at least 3 examples. They can be from any class on genetics!

How can the environment affect our genes? Give 3 examples (at least one not from class).

Complete the summary worksheet