Chapter 19, Problem 4SA

Summary Introduction

To determine:

The mode of X inactivation in female mammals which results in patchy coat color in calico cats.

Introduction:

X and Y are the chromosomes which are responsible for determining the sex of an individual. Females contain a pair of X chromosome and male contains two distinct sex chromosomes X and Y. X inactivation refers to the inactivation of one of the X chromosome resides in female mammals. It involves the silencing of gene which helps in transcription. There should be a balance between the number of copies of gene and level of gene expression. In human female there is one extra copy of X-linked gene, so to maintain the dosage compensation we need to inactivate one copy of X-linked gene. This results in equal expression of the gene.