Topic 3

Question 1

what are lethel alleles?

Answer 1

Lethality occurs when two copies of a mutant allele are inherited

Question 2

what is penetrance?

Answer 2

the % of individuals with a mutation that show the phenotype

Question 3

what is expressivity?

Answer 3

differing levels that a phenotype is expressed

Question 4

what are the reasons that individuals with the same mutation not show exactly the same phenotype?

Answer 4

1. environment
2. other genes/ genetic background
3. Subtlety of mutant phenotype – missed classification

Question 5

what happens if a gene ina pathway is mutated?

Answer 5

the phenotype will no longer be wildtype

Question 6

what are the three steps to determine the functional relationships between genes?

Answer 6

1. mutate a population to generate mutations in genes
2. perfome complementation tests to dtermine number of genes mutated
3. make double mutant lines to determine gene interactions

Question 7

in a complementation test, what does complement mean?

Answer 7

mutation is on an allele of different genes

Question 8

in a complementation test, what does fail to complement mean?

Answer 8

mutation is on alleles of same gene

Question 9

what is epistasis?

Answer 9

When the phenotype of a mutant allele masks the phenotype of the mutant allele of another gene

Question 10

what do supressor mutations do?

Answer 10

reverse the affect of mutation in another gene

Question 11

what is the result of a supressor mutation?

Answer 11

wildtype