Question

Describe how an individual could possess XY chromosomes, yet appear as a female.

Answer 1

When XY chromosome is present, the genotype is male. Y chromosome is present which has SRY gene which determines what gonads will be formed. If present, gonads are Testis. If absent, gonads are ovaries.

Testis contains two cells: Sertoli cells and Leydig cells. Sertoli cells secrete Anti-Mullerian hormone which causes regression of Mullerian duct, therefore female internal genitalia are not formed. Leydig cells secrete testosterone which performs two functions:

• Promotes the growth of Wolffian duct which forms the male internal genitalia (seminal vesicle, epididymis, ejaculatory duct and vas deferens).
• Convert into Dihydrotestosterone which will form male external genitalia.

When the males are RESISTANT to action of testosterone, the testosterone cannot act. Therefore, all the functions of testosterone are lost. Wolffian duct proliferation doesn't occur, therefore male internal genitalia is not formed. Dihydrotestosterone is not formed therefore, male external genitalia will not be formed. Therefore, external genitalia will resemble as females which is called Ambiguous genitalia (sex of baby cannot be determined by the external genitalia). This condition is called Androgen Insensitivity Syndrome, also known as Testicular Feminizing Syndrome).