2. SRY Gene
Testis-determining factor (TDF), also known as sex- determining region Y (SRY) protein, is a DNA-binding protein (also known as gene-regulatory protein/transcription factor) encoded by the SRY gene that is responsible for the initiation of male sex determination in humans. SRY is an intronless sex- determining gene on the Y chromosome in the placental mammals and marsupials, and mutations in this gene lead to a range of sex-related disorders with varying effects on an individual's phenotype and genotype

3. Crossing over during paternal meiosis prior to conception can cause SRY to be transferred from the Y chromosome to the X chromosome. The Y chromosome that results from this crossover is now lacking an SRY gene, and can no longer initiate testis development. When this chromosome is inherited from the father, the resulting offspring will have Swyer syndrome, characterized by a male karyotype (XY) and a female phenotype.

4. The X chromosome that results from this crossover event now has a SRY gene, and therefore the ability to initiate testis development. Offspring who inherit this chromosome will have a condition called XX male syndrome, characterized by an XX karyotype, and a male phenotype.

6. SRY has also been linked to the fact that males are more likely than females to develop dopamine- related diseases such as schizophrenia and Parkinson's disease. SRY encodes a protein that controls the concentration of dopamine, the neurotransmitter that carries signals from the brain that control movement and coordination.