Epistasis

Question 1

What is epistasis?

Answer 1

When one gene determines the expression of another gene.

Question 2

EXAMPLE.

What is the Widow’s Peak?.

Answer 2

In human’s a widow’s peak is controlled by one gene and baldness is controlled by other genes.
If you have alleles for baldness, you are bald. And it doesn’t matter if you have the alleles for widow’s peak because you have no hair.

Question 3

EXAMPLE.

So what does this mean?

Answer 3

The baldness genes are epistatic to the Widow’s Peak genes, as baldness masks the expression of the Widow’s Peak gene.

Question 4

EXAMPLE.

What 2 genes control flower pigment?

Answer 4

Gene 1 codes for yellow pigment - Y is yellow which is dominant.
Gene 2 codes for enzyme which turns yellow pigment orange - R is orange which is dominant.

Question 5

EXAMPLE.

What happens if you don’t have the Y allele?

Answer 5

The flower will be colourless despite if the R allele is present.

Question 6

EXAMPLE.

So what does this mean?

Answer 6

Gene 1 is epistatic to gene 2 as it masks expression of gene 2.

Question 7

Where are epistatic genes found on the locus?

Answer 7

Usually at different loci - different position on chromosomes.