The Y-chromosome is one of the two sex chromosomes, used to determine genotypic sex. Typically, females have two X (XX) chromosomes, while males usually have an XY pairing. Sperm may carry an X or Y chromosome. The Y-chromosome is contains the gene SRY, which triggers male development and is responsible for sperm production.
Humans have two possible sex chromosomes, X and Y. Typically, biological females are born with two X chromosomes while biological males have an X and a Y chromosome.
The Y chromosome accounts for nearly 2% of each cell’s DNA. The 50–60 genes on the Y chromosome are responsible for male development, such as the formation of the testes, as well as for sex determination and male fertility.
Since genes on the Y chromosome affect male development, changes to these genes can impact fertility. This is particularly the case for genes in the azoospermia factor (AZF) region of the Y chromosome, which contribute to the production and development of sperm cells. Deletions of one or more of these genes can impair sperm production, a condition called Y-chromosome microdeletion or Y-chromosome infertility.
Between 1 in 2,000 and 1 in 3,000 of men are affected by Y-chromosome infertility. In some cases, these men may still produce small numbers of sperm and may be able to conceive a child on their own. In other cases, sperm may potentially be retrieved from the testes and used in assisted reproductive technologies to help with conception.
Other chromosomal abnormalities, such as being born with an extra X (XXY, also known as Klinefelter syndrome), an extra Y chromosome (XYY), or both (XXYY) may also result in male infertility and other health issues.
Researchers believe that a pair of matching chromosomes evolved into the X and Y chromosomes in early mammals. Chromosomes were first identified during the late 1800s, and began to be better understood in the 1900s.
Since then, researchers have studied gene deletions to understand the structure and function of the Y chromosome. Around the 1980s, these deletions helped them describe the Y chromosome’s role in male infertility and sperm production. The Y chromosome’s SRY gene, which is responsible for male development, was then identified in 1990. Research is ongoing to better understand the Y chromosome’s effect on male health and fertility.