XY Chromosomes

Definition - What does XY Chromosomes mean?

The XY chromosomes are sex chromosomes that determine the male sex and are one of the 23 pairs of chromosomes in a human cell. Fertilization of an egg with a sperm containing a Y chromosome gives rise to an embryo with XY chromosomes which further develops to become a male fetus. XY chromosomes play a vital role in the sexual development of a male. Abnormalities of the XY chromosomes can impair the reproductive function leading to male infertility.

FertilitySmarts explains XY Chromosomes

A chromosome is a tightly packed DNA strand found inside the nucleus of the cell that carries genetic information in the form of genes. A human cell contains 23 pairs of chromosomes. The last pair of the chromosomes is called the sex chromosomes and its composition determines the sex of the individual. There are two types of sex chromosomes; X and Y. XY chromosomes are seen in males. Females have XX chromosomes.

Prior to normal cell division, also known as mitosis, the chromosomes double in number so that the two cells that result from division each contain 23 pairs of chromosomes. In contrast, during meiosis which takes place during the production of gametes, the egg and sperm cells, each gamete receives only one set of the chromosomes (23). Since females have two copies of X chromosomes, an egg always has an X chromosome. But there can be two types of sperm cells, one containing an X chromosome and one containing a Y chromosome. When an egg is fertilized by a sperm bearing a Y chromosome, the embryo develops to be a male fetus with XY chromosomes.

The XY chromosomes play the most important role in sexual differentiation, development of secondary sexual characteristics and the reproductive function in males. Abnormalities in these sex hormones can impair sexual features, sexual activity, hormone levels and production of sperm causing infertility.

Abnormalities of XY chromosomes can be in the number or in the genes that these chromosomes carry. Common abnormalities include the presence of an extra X chromosome in a male (XXY) giving rise to Klinefelter syndrome and the presence of an extra Y chromosome causing double Y syndrome. These males are usually sterile or subfertile.

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