Updated by: Arabinda Naik
TDF (Testes Determining Factor) gene is the gene present on the Y chromosome in mammals. Y chromosome is present in males but absent in females so, it helps in male sex determination and induces the undifferentiated gonads to form testes (male reproductive organ). SRY gene: Humans have 23 pairs of autosomes and one pair of sex chromosomes. The Y chromosome is a male determining gene. The Y chromosome is one of the smallest chromosomes in humans. It has the least number of genes that are 55 genes, and the X chromosome has about 900 genes. The Y chromosome represents about 2-3 percent of the total DNA in the cells. The Y chromosomes consists of a male determining gene the SRY gene that causes testis to form in the embryo and forms the development of external and internal male genitalia. If there is a mutation in the SRY gene, the embryo will develop female genitalia despite containing XY chromosomes. The Y chromosomes has a limited number of genes because the chromosomal genes have degenerated during evolution. The Y chromosome is also known as the gene poor chromosome.