This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetics, Subject name: Pathology
[{'content': 'Testis determining gene/sex determining region is located on: \nSelect and explain. \nA. X chromosome, B. Y chromosome, C. Chromosome 21, D. Chromosome 18', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans: b (Y chromosome) Ref: Robbins, 7th ed,p. 181, Ganong, 22nd p. 411Y chromosome is necessary for the development of testes. The testes determining gene (SRY - sex determining region on Y chromosome) is located near the tip of the short arm of Y chromosome. This SRY is a DNA binding protein, it bends the DNA and initiates transcription of a cascade of genes necessary for testicular differentiation, including the gene for MIS During normal gametogenesis, as a consequence of meiosis each ovum contains one X chromosome, but half of the sperms contain an X chromosome and half contain a Y chromosome. When sperm withY chromosome fertilizes ovum, genetic male results. When sperm with X chromosome fertilizes ovum, genetic female results.', 'role': 'assistant'}]