Chapter 12, Problem 11STP

Summary Introduction

To explain:

The cause for coat color variations in females of some animals.

Introduction:

Human females have 22 pairs of autosomes and one pair of X chromosomes. Females have two doses of X chromosomes while males have only one dose. To balance the difference in the dose of X- related genes, one of the X chromosomes stops working or becomes inactivated. This is called dosage compensation and is a random event.

Answer to Problem 11STP

The random inactivation of a particular X chromosome causes the coat colors in females of some animals.

Explanation of Solution

The coat colors of some animals like the calico cat is caused by random inactivation of X chromosome. The resulting colors depend on the X chromosome that is activated.

For example a calico cat has orange and black patches. One X chromosome codes for orange fur and another code for black fur. The orange patches in the cat are formed due to inactivation of X chromosome carrying the allele for black coat color. Similarly the black patches are formed due to inactivation of X chromosome carrying the allele for orange coat color.