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X Chromosome

The X chromosome is one of the two sex chromosomes that are found in humans, the other being the Y chromosome. These sex chromosomes are among one of the 23 pairs of human chromosomes that comprise man’s genetic make up. The X chromosome has about 155 million base pairs that are essentially the DNA’s building blocks. These pairs represent about 5 per cent of the DNA that are found in human cells.

Normally, each person’s cells contain one pair of sex chromosomes. Females have two X chromosomes and males have an X chromosome and a Y chromosome. During the early stages of the embryonic development of a female, one of the two x chromosomes is permanently (but randomly) shut down or turned off in the somatic cells. This process is called the X-inactivation or Lyonization. This process of turning off the extra X chromosome is performed by the body to make sure that females, along with males, will only have one working copy of the X chromosome in their cells.

One of the most active branches of genetic research is the attempt to try and identify the genes on each chromosome. Each genetic researcher have their own unique approaches to try to predict the number of genes that are contained in a chromosome and because of this the estimations for the total number of genes would vary with each research. Based on estimates, the X chromosome may contain between 900 and 1400 genes.

Web Resources On X Chromosome

What is the X chromosome?
Human Chromosome X

Book Resources On X Chromosome

Genetic Analysis of the X Chromosome by Henry F. Epstein
The genetic control of X chromosome choice in X inactivation by Lisa Helbling Chadwick

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