1. How does the ENVIRONMENT affect the traits of organisms?
Are you just your DNA?
How does the
ENVIRONMENT
affect the traits of
organisms?

2. How does the environment affect the traits of organisms?
1. The environments influences the expression of traits by chemically interacting with DNA in the cell, or by limiting available resources the organism requires to express the gene.
Ex. The gene for the dark pigment in coat color for Siamese cats is activated by colder temperatures.
Because of this, only the coolest parts of the body-- the feet, tail, and face– express the dark color fur

3. Snowshoe Hare
Brown in summer
White in winter
My DNA does NOT change every season…the temperature just makes the pigment in the hair come out DIFFERENT
So I blend in with my environment…harder for predators to catch me for dinner!!

4. Because they cause MUTATIONS!!
2. Environmental hazards can create genetic mutations , turning off or altering the expression of a gene. These hazards are called mutagens.
Ex. Environmental toxins mimic human hormones such as estrogen and inhibit the production of that hormone by cells
Because they cause MUTATIONS!!

5. Identical Twins are used to study the effect of environment on gene expression. This is because identical twins have identical genes but are often exposed to different environments.

7. Causes and Effects Disease/Cause
Cause and Effect relationship between the environment and the expression of genetic traits
Lung/Mouth Cancer & Tobacco Use
■Tobacco products contains toxins and carcinogens
■Carcinogens can cause mutations in the DNA leading to uncontrolled cell division (cancer)

9. Skin Cancer & Sun Exposure
Disease/Cause
Cause and Effect relationship between the environment and the expression of genetic traits
Skin Cancer & Sun Exposure
■Skin cancer is directly linked to sun exposure because UV light mutates the DNA, causing cancer
■Sunlight also destroys folate (folic acid) when absorbed by skin. Folic acid is key to DNA repairing its mutations.
■Folic acid deficiency is a contributor to skin cancer but can be found in vitamins.
■Sun exposure gives us vitamin D, a vitamin that helps prevent heart disease. However, you only need 10 minutes of exposure a day for this benefit…or you can take a vitamin!!

11. Diabetes & Diet/Exercise ■Linked to diet and exercise
Disease/Cause
Cause and Effect relationship between the environment and the expression of genetic traits
Diabetes & Diet/Exercise
■Linked to diet and exercise
■It is possible to delay or prevent type 2 diabetes by exercising and losing weight
Heart Disease & Diet/Exercise
■Different genes respond differently to changes in diet and health choices
■So far, 40 or more genes have been identified that are linked to cardiovascular health

12. Carriers What is a carrier?
A person or organism that has inherited a genetic trait or mutation, but does NOT have the genetic disorder.
They have only 1 copy of the ‘bad’ gene.
They can pass the trait to their offspring.

14. Autosomal Genetic Disorders
Occur when the gene defect is on one of the first 22 pairs of chromosomes. – THE AUTOSOMES
1. Huntington’s Disease
~Autosomal Dominant Gene
~Breaks down certain areas of the brain
~Symptoms begin mid to late 40’s
You only need 1 copy of the bad gene!

15. Sickle Cell Anemia 2. Sickle Cell Anemia: Codominant autosomal gene
2. Sickle Cell Anemia:
Codominant autosomal gene
Leads to misshapen red blood cells, which lead to poor circulation and pain.
Heterozygous (carrier) individuals are NOT afflicted with sickle cell and they are resistant to malaria

17. Cystic Fibrosis 3. Cystic Fibrosis
3. Cystic Fibrosis
Recessive autosomal gene – must have TWO copies of bad gene
Leads to mucus build up in lungs and digestive tract which may be fatal

18. Tay-Sach’s 4. Tay-Sach’s Recessive autosomal gene
4. Tay-Sach’s
Recessive autosomal gene
Degenerates (breaks down) the central nervous system, leading to premature death

19. PKU 5. PKU (Phenylketonuria) Recessive autosomal gene
5. PKU (Phenylketonuria)
Recessive autosomal gene
Leads to the inability to break down the amino acid phenylalanine when ingested
The phenylalanine builds up in the brain and leads to decreased mental function
If detected early, it can be controlled by diet
Individuals with PKU cannot eat foods/drinks with phenylalanine (breads, dairy, proteins, etc.)

20. Practice EOC Questions
One of the parents of a child has PKU, which is caused by recessive alleles. The other parent does not have the PKU alleles. What is the chance that the couple will have a child with phenylketonuria? 0%
50%
75%
100%

21. Practice EOC Questions
Which cross would be represented as Aa x aa, where (A) is a dominant allele and (a) is a recessive allele?
Cross
Parental Feather Colors
Offspring Feather Colors 1
White x White
100% White 2
75% White, 25% Dark 3
White x Dark
50% White, 50% Dark 4
Dark x Dark
100% Dark

22. Practice EOC Questions
If Jeanette is a carrier for sickle cell and has a baby with Juan, who is also a carrier, what is the probability that their child will be born with sickle cell anemia?___________________
What is the probability that their child will be a carrier? ___________________

23. Practice EOC Questions
Huntington’s disease is a dominant trait. What are the chances that a child will develop Huntington’s disease if both parents are heterozygous for the trait?
A. 0 out of 4
B. 1 out of 4
C. 2 out of 4
D. 3 out of 4

24. Practice EOC Questions
Himalayan rabbits carry the C gene, which is required for the development of pigments in the fur, skin, and eyes. The C gene is maximally active from 15°C to 25°C and inactive above 35°C . This gene expression produces rabbits with a distinctive coat coloring. Why do the Himalayan rabbits exhibit different colors of fur?
A. The environment determines whether the gene for fur pigmentation is expressed.
B. The genetic makeup of the rabbits change.
C. The rabbit’s color changed in order to attract a mate.
D. The rabbit’s cells undergo mitosis.