<prompt> The Y chromosome carries a gene on its sho arm that codes forTestosteroneMIFTestes-determining factor TDFProgesterone  <response>: The SRY sex region Y chromosome gene present on the sho arm of the Y chromosome codes for TDF Testes Determining Factor. Presence or absence of this chromosome decides whether the fetus will be male or female. Sex determination is not possible till week 6 i.e. why the embryo is called indeterminate embryo till week 6. External sex differentiation completes after week 11. USG sex determination can be done at this time. 