Which statement most accurately describes how the sex of a human embryo is determined?
1) Embryos with a genital tubercle become male; embryos without the tubercle become female.
2) Embryos with one X chromosome become male; embryos with two X chromosomes become female.
3) Embryos exposed to estrogen become female; embryos exposed to testosterone become male.
4) Embryos with the SRY gene become male; embryos without the gene become female.