In a developing fetus, what influences whether it is going to become male or female? What influences the cells to start building male or female organs?

Question

In a developing fetus, what influences whether it is going to become male or female? What influences the cells to start building male or female organs?

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Answer 1

as an embryo is developing, there will eventually be a “check” for a specific gene on the Y chromosome called the SRY gene. this occurs around the 6th week of pregnancy, and it acts as the trigger for a whole bunch of other genes to activate and start developing the male sex organs, while also suppressing the development of female sex organs. if the SRY gene is absent (like in typical females, no Y chromosome = no SRY), or defective (someone with XY but the SRY gene doesn’t work for some reason), the embryo will go on to develop as a female. this is why you might have heard the factoid that we all start off as females during development.