The human genome is said by some to be the "book of life," and the X-chromosome a large part of the the plot. A team of genome researchers have described the nature of this mysterious "chapter" in the DNA story.
Dr. Steven Scherer, associate professor in the Baylor College of Medicine department of molecular and human genetics and director of mapping in the BCM Human Genome Sequencing Centre, says large numbers of medically related genes happen to fall on the X-chromosome, and for a chromosome that is bereft of genes compared to other chromosomes, it is well characterized with regard to disease genes.
Scherer and his colleagues in the BCM Sequencing Centre were the number two contributors to the sequencing effort directed at the X chromosome. It was led by the Wellcome Trust Sanger Institute in Britain.
Dr.Scherer says he has expectations that this chromosome is the all-star of the series and will make interesting reading for the general scientific population and the lay public; he says if a person was going to read a chromosome paper, this probably ought to be the one to read.
The role of the X and Y chromosomes has been evolutionary, and way before the split between birds and mammals, the X and Y chromosomes were just like any other pair of chromosomes - each was fairly similar and carried similar information.
While tracing the evolution of the X chromosome, the research showed that slowly, but surely, the Y chromosome "dropped off the face of the earth," said Scherer, and became almost like the appendix of the human genome.
Each woman has two X chromosomes, each man has an X chromosome and a Y chromosome. In women, one of the X chromosomes is largely inactivated. Because there are actually few genes on the Y chromosome, inactivating most of one of the X chromosomes in women means that men and women each have one active X chromosome, where most of the coding information exists.