If you’re trying to conceive, your partner’s sperm count is probably something that’s always on your mind. A home test like the SpermCheck Fertility can provide general reference values for a normal, low or very low sperm count.
If a sperm carrying the Y chromosome reaches an egg first, it will determine the baby’s sex. Scientists believe that Y-chromosome sperm can zip through the thick cervical mucous more quickly.
What is the Y chromosome?
The Y chromosome is one of the 23 pairs of chromosomes that make up a human cell. It is found only in males and contains genes for determining the sex of offspring during sexual reproduction. In the vast majority of therian mammals, the Y chromosome is responsible for triggering the development of male body parts in embryonic development, while the X chromosome is responsible for determining female sex.
Unlike the other chromosomes, the Y chromosome is unable to undergo genetic recombination during meiosis. Without this recombination, genes on the Y chromosome degenerate over time and are eventually lost from the genome. However, recent studies have shown that the Y chromosome has evolved mechanisms to “put the brakes on”, slowing the rate of gene degradation down to a possible standstill.
To study this, researchers led by Daniel Winston Bellott, a biologist at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, examined the Y chromosomes of eight different mammals, including humans, chimpanzees, monkeys, rats, mice, bulls, and mole voles. They discovered that many of the Y chromosome genes shared similarities across species, suggesting they are essential for mammalian survival. Further analysis revealed that most of these genes were dosage-dependent, meaning they require two copies of the gene to function. This suggests that the Y chromosome may still have the power to do much more than just determine the sex of a developing fetus.
How does the Y chromosome work?
The Y chromosome is so isolated, in fact, that genes on it don’t get the chance to swap DNA with the X chromosome during sexual reproduction. Without this recombination, genes on the Y chromosome are prone to mutation and ultimately degrade over time. But recent studies show that the Y chromosome has developed some pretty convincing mechanisms to put the brakes on this gene degradation and potentially slow it to a stop.
Scientists recently compared the Y chromosomes of 62 men and found that there was an extremely high rate of “gene conversion events” within palindromic sequences (DNA sequences that read the same forwards as backwards, like the word “kayak”). This is basically a copy-and-paste process that allows damaged Y chromosome genes to be repaired using an undamaged back-up copy as a template.
Researchers also found that most of the genes on the Y chromosome were dosage-dependent, meaning that they required two copies to function properly. This could help explain why the Y chromosome has remained relatively stable over evolution, despite the fact that it is no longer able to swap DNA with the X chromosome via sexual reproduction. The Y may still be a little lonely, but it seems to have the tools it needs to prevent its collapse into obscurity. This is particularly important because many of these Y chromosome genes appear to have functions that are crucial for human health.
What if my Y chromosome is not normal?
Men with Y chromosome deletions may have difficulty producing sperm. They can experience azoospermia (no mature sperm cells), oligospermia (fewer than normal number of sperm cells) or asthenozoospermia (sperm with abnormal morphology). They also have a higher risk for a blockage in the tubes and may require a vasectomy, or other male factor infertility treatments such as ICSI or TESE.
The Y chromosome does not mix with the X chromosome during sexual reproduction, so its genes are transmitted linearly from father to son. This means that the Y chromosome can tell whether a baby will be male or female.
Genetics and lifestyle factors can impact the Y chromosome. The most important factor is timing. Having sex close to ovulation allows the faster Y chromosome sperm to make it to the egg before it dies, and increases the chances of fertilization.
Other genetic factors that can affect Y chromosome production include Klinefelter Syndrome and other X chromosome problems. These can be diagnosed with a karyotype test and a Y chromosome test. In addition, all men with azoospermia and oligospermia should be screened for Y chromosome deletions. These can be detected with a simple semen analysis at home using the two-strip lateral flow immunochromatographic test. Semen analyses should follow WHO guidelines for examining and processing semen.