Chapter 3, Problem 10P

Summary Introduction

To analyze:

The number of Barr bodies in female and male nucleus.

Introduction:

The first visualization of Barr body was by Murray Barr-$\text{1949}$. Barr body is a dense structure of chromatin, forms in the nuclei of female somatic cells. In humans, females have two X chromosomes and males have one X and one Y chromosomes. The sex cells or gamete cells are the only cells that take part in sexual reproduction while the remaining cells are called somatic cells that do not participate in the process. In females, one X chromosome is active while another X is inactivated through the process of lionization, and it becomes a Barr body. In order to have an equal amount of X chromosome expression in both males and females, X inactivation is necessary; otherwise the amount of genetic information expressed will be two fold or more. The selection of X chromosome to be inactivated is random, but once the active and inactive X chromosomes are selected, the descendent cells will have the same X chromosome active and inactive.