Y chromosome

From ArticleWorld

The Y chromosome is one of the sex chromosomes in mammals. It is a component of the process of sex determination and is carried by the males. It has the gene that stimulates the development of the testis. This chromosome is useful as it can determine paternal linkages and it is also the cause of the fewest genetic disorders in humans. Normally individuals contain one pair of sex chromosomes, with males showing the XY condition and females the XX condition.

Origins

The X and Y chromosomes appeared about 350 million years ago. They developed when a reptile developed a gene making its owners male. The chromosome having this gene became known as the Y chromosome and the one without it the X. Today there are still some reptiles without these genes and sex is determined by environmental conditions. Eventually recombination between these two chromosomes was ceased as this was harmful to both sexes. With this function lost, it became difficult to get rid of mutations on the Y chromosome that were dangerous and there was damage to some genes until they became useless and were removed from the Y chromosome.

Diseases

There are no vital genes on the Y chromosome as it is only possessed by half of the population. However there is a disease that can affect the Y chromosome resulting in a defect in the development of the testis. This condition results in the production of a female phenotype or physical appearance but infertility due to the absence of the second X chromosome. It is possible though for there to be multiple copies of the Y chromosome and this is called aneuploidy. This condition is associated with a tall stature and learning disabilities in men with only one extra copy. Others that have more than one extra copy tend to have delayed physical development, skeletal abnormalities and slow learners.