Lecture 42

Question 1

When there’s no interaction, and two genes independently contribute to phenotype, what is the ratio. What might this indicate?

Answer 1

9:3:3:1 in F2

for example, two independent autosomal genes on different chromosomes

indicate: two genes, autosomal, different chromosomes, no interaction

Question 2

What are complementary genes? What ratio would the F2 generation have? What interpretations can you draw from this?

Answer 2

both genes are needed to produce a WT phenotype

9:7

interp: two autosomal genes, dominance w1+ > w1-, w2+ > w2-, complementary gene action, both genes required in series

Question 3

What is an example of complementary genes?

Answer 3

harebell petal colour

blue = WT (requires w1+ and w2+)

white = mutant

F2 ratio is 9 blue 7 white

Question 4

What are duplicate genes? What is the ratio involved? What is the interpretations?

Answer 4

either gene alone can produce the WT phenotype

15:1

2 genes with the same function, one WT allele at either locus restores function, pathway: redundant or parallel pathways

Question 5

Give an example of duplicate genes

Answer 5

wheat seed coat colour

red = WT
white = mutant
F2 ratio = 15 red:1 white

Question 6

dominance is allele conceals allele. What is epistasis? What are the ratios involved with recessive epistasis and dominant epistasis?

Answer 6

gene conceals gene

recessive: 9:4:3

dominant: 12:3:1

Question 7

What is recessive epistasis?

Answer 7

when the recessive phenotype of one gene conceals the phenotype of a second gene (i.e. the biochem pathway halts at the first step)

Question 8

What is dominant epistasis?

Answer 8

when the dominant phenotype of one gene conceals the phenotype of another gene (complicated pathway)