6 - Molecular basis of gene interaction

Epistasis

Interaction between two or more genes to control a single phenotype

The epistatic gene

Doing the masking

The hypostatic gene

Masked gene

What can epistatic ratios allow geneticists to determine

Order of genes in a particular pathway

Ratio for dominant epistasis

12:3:1

Ratio for complementary gene action

9:7

Ratio for duplicate gene action

15:1

Ratio for dominant suppression epistasis

13:3

Dominant epistasis

Dominant allele of one gene masks the effect of both alleles of another gene

Complementary gene action

2 genes work together to produce a trait that is impossible if either gene is missing

Duplicate gene action

Double dominant alleles so two genes working on the same part of the pathway

Dominant suppression epistasis

Some genes have the ability to suppress the expression of a gene at a second locus

Human example of epistasis

Bombay phenotype