Chapter 11, Problem 16A

Summary Introduction

To explain:

How epistasis causes the differences in coat color in Labrador retrievers

Introduction:

Genetic disorders result from inheritance of traits which are either dominant or recessive. The basic patterns of human inheritance follow Mendel’s law of inheritance but there are some complex inheritance of traits that do not follow inheritance pattern described by Mendel. Epistasis is one such disorder.

Answer to Problem 16A

Epistasis is an interaction produced due to one allele hiding the effects of another allele. The coat color in Labrador retrievers is due to interaction of two genes each with two alleles. The dominant allele ( E ) determines whether the fur will have dark pigment. The dominant allele ( B ) determines how dark the pigment will be. Different combinations of these alleles produce different colors of the coat.

Explanation of Solution

Coat color in Labrador retrievers vary from yellow to black. This variety of colors is produced due to one allele hiding the effect of another allele in an interaction called epistasis.

The coat color in Labrador retrievers is controlled by two sets of alleles. The dominant allele ( E ) determines whether the fur will have dark pigment. The fur of the dog with genotype ee will not have any pigment. The dominant allele ( B ) determines how dark the pigment will be. If the dog’s genotype is EEbb or Eebb , the dog’s fur will be chocolate brown. Genotypes eebb , eeBb , and eeBB will produce a yellow coat, because the e allele masks the effects of the dominant B allele.