Lecture 11 - Interactions Between Alleles & Genes, Penetrance And Expressivity

Question 1

What occurs in dominance/recessive interactions between alleles?

Answer 1

Wild type (functional protein) = dominance and Mutant type (non functional/unstable protein) = recessive

Question 2

What is incomplete dominance?

Answer 2

Heterozygotes showing an intermediate phenotype such as red (dominant) x white (recessive) = pink

Question 3

What is codominance?

Answer 3

Heterozygotes show both alleles: Human MN blood group has M, N and MN types

Question 4

What occurs when there are multiple (2+) alleles?

Answer 4

Dominance hierarchy is created

Question 5

What is pleiotropy?

Answer 5

One gene contributing to more than one trait:
- gene involved in cilia AND flagella function if mutated

Question 6

What are lethal alleles?

Answer 6

Alleles that if occur mean offspring die (eg AA is lethal while Aa and aa aren’t)
- can skew phenotypic ratios

Question 7

What is sickle cell syndrome an example of?

Answer 7

Complications with dominance and pleiotropy:
- physiological incomplete dominance
- biochemical codominance

Question 8

What is epistasis?

Answer 8

One allele masking the affect of another on a different gene

Question 9

What tests can determine if a phenotype arises from mutations in the same or separate genes?

Answer 9

Complementation tests that involve crossing 2 of the same phenotype and if the mutation is on separate genes, the other phenotype is present

Question 10

What is penetrance?

Answer 10

Measures the percent of individuals with a given genotype that exhibit the associated phenotype

Question 11

What is expressivity?

Answer 11

Measures the extent to which a given genotype is expressed at phenotypic level