The SRY gene is a y linked sex determining gene. The SRY gene encodes for male genitalia. The SRY gene is located on one exon. The SRY gene is pleiotropic as it encodes for multiple traits related to male sexual development. If one were to have two x chromosomes but an SRY gene they would have male genitalia (testes). If one were to have the x and y chromosomal pair, but no SRY gene they would have female genitalia (ovaries). Also, if one were to have any sex linked chromosome combination with an SRY gene but the SRY gene is rendered inactive (due to a mutation) they would have female genitalia.
The SRY gene was discovered in 1985 by studying the DNA sequences of a person with ovaries and a XY gene and 3 people with testis and XX genes. This supported a long held theory that having male genitalia was not a consequence of having a Y chromosome but having a specific gene on the chromosome. The development of human sex charactaristics and it's linkage to specific genes remains largely a mystery.
Recently researchers in Japan have discovered another piece in mouse SRY. This second piece of mouse SRY, SRY-T, consists of two exons. This SRY-T also seals "instability sequences" on the end of SRY preventing it in degrading, meaning SRY-T is just as crucial for the development of testis as SRY. So the same differences in phenotype when displacing the SRY gene also occur when displacing the SRY-T gene, this was confirmed by researchers at the University of Queensland by using CRISPR. I think this new discovery of a male genitalia linked gene will give us more insight into the development of sex characteristics of both male, female and intergender people.