AM - Polygenic Inheritance

Question 1

What is polygenic inheritance?

Answer 1

The inheritance of a trait governed by more than one gene

Question 2

What are the 3 main features of polygenic inheritance?

Answer 2

1. Continuous variation (e.g height, weight, colour)
2. Usually quantified by measurement
3. Multiple genes will have an additive effect

Question 3

What is an example of multiple alleles?

Answer 3

Human blood groups

Question 4

What is penetrance?

Answer 4

The proportion of individuals showing the expected phenotype

Question 5

What is expressivity?

Answer 5

Degree of expression of phenotype in an individual

Question 6

What can alter expressivity? (2)

Answer 6

1. Temperatute (In rabbits)
2. Nutrition (Lactose intolerance)

Question 7

What is pleiotropy?

Answer 7

The phenomenon in which a single locus affects two or more apparently unrelated phenotypic traits

Question 8

What is an example of pleiotropy?

Answer 8

All white cats are deaf

• White fur colour is caused by a lack of melanocytes
• Melanocytes also regulate correct ion balance for transmission of signals to the brain