* Sex Chromosomes: Humans have 23 pairs of chromosomes, with one pair being the sex chromosomes. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).
* SRY Gene: The Y chromosome contains a gene called SRY (Sex-determining Region Y). The SRY gene is responsible for initiating the development of male characteristics.
* Absence of SRY: In the absence of the SRY gene (as in an XX embryo), the embryo will develop along the female pathway. This pathway is not simply a "default" but is actively driven by other genes on the X chromosome.
* Hormonal Influence: The ovaries, which develop in the absence of SRY, produce hormones like estrogen and progesterone, which play crucial roles in female development.
In summary: The presence of two X chromosomes in an embryo, without the presence of the SRY gene on the Y chromosome, triggers the cascade of events that lead to the development of a female.
