The chromosome that determines male gender in microdeletion studies – the Y chromosome – is the carrier of genetic material. There are 23 pairs (i.e. 46) of human chromosomes, 22 of which are autosomes, the same for both males and females; the remaining pair are sex chromosomes, the female chromosome consists of two identical chromosomes, written as XX, and the male one consists of an X chromosome and a Y chromosome, written as XY, and the Y chromosome is the chromosome that determines male sex. According to the World Health Organization, 10% of couples in the world suffer from infertility, male infertility accounts for about half of them, and more than 30% of them are caused by genetic abnormalities. microdeletion of the Y chromosome is the main genetic factor leading to male infertility. In 1976, Tieplolo and Zuffardi found that patients with azoospermia had a deletion in the long arm of the Y chromosome (Yq1 chromosome deletion 1), so they called this site the azoospermia factor (AZF). At least three spermatogenic sites (AZFa, AZFb, and AZFc) have been identified, located proximal, intermediate, and distal to Yq11. Y chromosome microdeletions occur in multiple genes associated with AZF on the Y chromosome. Although the detection rate varies relatively widely due to different selection criteria of test subjects in each laboratory, the frequency of deletions in each region is basically stable: Azfc accounts for 79% of the total deletions, Azfb for 9%, Azfa+b for 6%, Azfa for 3%, and Azfa+b+c for 3%. Microdeletions of these genes will lead to sperm disorders, oligospermia, weak sperm, azoospermia and infertility. Studies have shown that Y chromosome microdeletions are due to genetic recombination, which is associated with a large number of highly repetitive and palindromic sequence features on the y chromosome. y chromosome microdeletions can be passed down from normal sperm with microdeletions. It can also occur through normal sperm after fertilization during embryonic development with microdeletions of the Y chromosome. Alternatively, modern artificially assisted reproduction techniques may pass down the Y-banded chromosome. Inheritance and Phenotype Azfa has the lowest frequency of deletions, but the most severe consequences. In most cases the entire Azfa deletion occurs, manifesting as severe oligospermia and support cell only syndrome. There is an association between surname and Y chromosome type Azfb and Azfb+c also manifest as azoospermia or oligospermia. The chances of obtaining spermatozoa by means of testicular biopsy, for example, are almost zero for either whole Azfa or Azfb deletion, or Azfb+c deletion. Puncture and ovulation promotion of the female partner are recommended unnecessarily in such patients. The needless financial burden and various complications can be reduced. Azfc has the highest frequency of deletions and the situation is relatively positive. Sperm counts in deletions range from none to normal, but are usually accompanied by abnormal sperm morphology. Studies by the European Reproductive Society have shown that azoospermia patients due to Azfc deficiency generally have better results with assisted reproduction using techniques such as ISCI. However, Azfc deficiency can also occur in the male offspring of these patients. Screening population Who needs to be screened for Y chromosome microdeletion? Patients with azoospermia, oligospermia, weak spermatozoa and patients with unexplained disorders, as well as men with unexplained habitual miscarriage of their spouses need to be tested for Y chromosome deletion. Later studies found that for Azfc deletion, which accounts for the largest percentage, the sperm count of the patient can range from azoospermia to normal. So a normal sperm count does not necessarily mean that there are no Y chromosome microdeletions. Y chromosome microdeletions have also been detected in patients with azoospermia and oligospermia (testicular lesions, obstructive azoospermia, varicocele) with chromosomal alterations (aneuploidy, deletions, translocations) and in patients with normal karyotype but severe phenotypic abnormalities. The detection of Y chromosome deletions is required for both unexplained and definite male infertility, especially when intracytoplasmic sperm injection and other assisted reproductive treatments are performed. In developed countries in Europe and the United States, Y chromosome microdeletions have become a routine test for male infertility. If a male infertility patient has a Y chromosome microdeletion, general medication is ineffective. The use of Y chromosome microdeletion testing products can directly detect Y chromosome microdeletion at the genetic and molecular level, providing a strong diagnostic basis for intracytoplasmic single sperm injection and other assisted reproduction techniques. The treatment for the deletion or the presence of the deletion varies from locus to locus. The results of the test will guide the physician on whether to use intracytoplasmic single sperm injection for assisted reproduction; and provide a basis for selective transfer of female embryos, as the male offspring will inherit the father’s infertility defect. The test is very convenient for the patient as it only requires a small amount of blood to be drawn.