Lecture 14: Gene Interaction pt2

What is recessive epistasis?

Recessive epistasis occurs when the homozygous recessive of one gene covers all phenotypes of another gene.

What is the phenotypic ratio for a dihybrid heterozygous cross involving recessive epistasis?

The phenotypic ratio is 9:3:4.

What is double recessive epistasis?

Double recessive epistasis occurs when the homozygous recessive genotypes of either gene result in the same phenotype.

What is the resulting phenotypic ratio in a dihybrid cross involving double recessive epistasis?

The resulting phenotypic ratio is 9:7.

In double recessive epistasis, what happens if you have homozygous recessive alleles for either gene?

You will get a white color since the homozygous recessive genotype covers up any other color.

What defines dominant epistasis?

Dominant epistasis is when one allele for a dominant trait covers up everything else and controls the phenotype.

What is the phenotypic ratio resulting from a dihybrid heterozygous cross involving dominant epistasis?

The phenotypic ratio is 12:3:1.

In dominant epistasis, what does the presence of a dominant allele indicate?

The presence of a dominant allele indicates that it controls the phenotype regardless of other alleles.

What is double dominant epistasis?

Double dominant epistasis occurs when both genes code for the exact same outcome, allowing for similar dominant expression.

What is the phenotypic ratio for double dominant epistasis in a dihybrid cross?

The phenotypic ratio is 15:1.

What is dominant recessive epistasis?

Dominant recessive epistasis occurs when the dominant allele of one trait and the homozygous recessive of another trait give the same phenotype.

What is the phenotypic ratio for dominant recessive epistasis?

The phenotypic ratio is 13:3.

How do you determine which gene is epistatic?

The problem must explicitly state which gene is epistatic.

What is the significance of the 16 offspring in dihybrid heterozygous crosses related to epistasis?

A total of 16 offspring indicates a dihybrid heterozygous cross is being performed.

What can cause a purple flower in the context of epistasis discussed in class?

A purple flower is produced when both genes involved have functional dominant alleles.

What happens if both genes involved in epistasis are homozygous recessive?

If both genes are homozygous recessive, it results in a lack of the expected color, such as white.

In epistatic interactions, what is the result if one gene is epistatic to another?

The epistatic gene controls the phenotype by masking the effects of the other gene.