10. Non-Mendelian inheritance patterns

Question 1

Define the following terms: epistasis, pleiotropy, polygenic.

Answer 1

• variations of Mendelian inheritance
• epistasis: one gene masks another gene (colour in labs)
• pleiotropy: one gene affects many unrelated body parts (e.g. sickle-cell disease, cystic fibrosis, Marfan syndrome)
• polygenic: trait influenced by many genes (height, weight, skin colour)

Question 2

Give an example showing that gene expression is influenced by the environment.

Answer 2

e.g. coat color in Himalayan rabbits and Siamese cats

• an allele produces an enzyme that allows pigment production only at temperatures below 33C. Extremities of Himilayan cat are cooler (melanin is produced)

Question 3

What are symptoms of cystic fibrosis?

Answer 3

1. salty-tasting skin
2. poor growth and poor weight gain despite normal food intake
3. accumulation of thick sticky mucus
4. frequent chest infections
5. coughing or shortness of breath.
6. males can be infertile due to congenital absence of the vas deferens

Question 4

What are symptoms of Marfan syndrome?

Answer 4

connective tissue defect
- affects the eyes, heart, skeleton, and blood vessels
- usually long and thin bodies with long legs, arms, fingers, and toes

Question 5

What are symptoms of Sickle cell anemia?

Answer 5

mutations in the beta-globin deforms red blood cells
- irregular shape causes clustering together, forming a block in the veins (blocks blood flow)
- results in health problems and causes damages to the heart, brain, and lungs.