The principle of blood test in Hong Kong is that Y chromosome is the most representative sex chromosome. A pair of male sex chromosomes consists of an X chromosome and a smaller Y chromosome. It contains SRY gene, which can trigger the occurrence of testis and thus determine male traits. The human Y chromosome contains about 60 million base pairs. Genes on the Y chromosome can only be passed down from generation to generation, so the pedigree of genes remains on the Y chromosome. With the continuous exploration of DNA technology, Y-DNA analysis has been applied to various fields of medicine.

Hong Kong DNA Y chromosome detection If the venous blood on the pregnant woman's arm is taken to detect the SRY chromosome, the xy of the fetus can be known in advance. At present, it is recognized by the international medical community as the safest, timely and accurate identification method. With the development of DNA detection technology, it can be detected when the embryo length reaches 10mm in the seventh week of pregnancy.