Gene Interactions

Question 1

What is epistasis?

Answer 1

When the alleles of one gene mask the phenotypic effect of another gene

Question 2

What is the epistatic allele and the hypostatic allele?

Answer 2

The epistatic allele masks the presence of the others, and the hypostatic allele is the one masked

Question 3

What is the F2 phenotypic ratio seen for duplicative recessive epistasis? Why do we get this ratio?

Answer 3

9:7. If either gene is homozygous recessive, it masks the presence of the other gene

Question 4

What is the F2 phenotypic ratio seen for duplicative dominant epistasis? Why do we get this ratio?

Answer 4

15:1. Gene redundancy, alleles in either gene can give the WT phenotype, so the only way to get a mutant phenotype is for both to be homozygous recessive

Question 5

What is the F2 phenotypic ratio seen for dominant epistasis? Why do we get this ratio?

Answer 5

12:3:1. The presence of a dominant allele of one gene masks the presence of any alleles of the other gene, all it takes is a single copy to get that phenotype

Question 6

What is the F2 phenotypic ratio seen for recessive epistasis? Why do we get this ratio?

Answer 6

9:3:4. If one particular gene is homozygous recessive, it masks the presence of the other gene. We get this a lot for biosynthetic pathways, because it doesn’t matter if the gene further on is working because the one before isn’t working