Changes

* The foetus receives its genetic endowment in two equal portions from the male gamete ('''Spermatozoon''') and female gamete ('''Oocyte''').

* The foetus receives its genetic endowment in two equal portions from the male gamete ('''Spermatozoon''') and female gamete ('''Oocyte''').

* The X sex chromosome is larger than the Y sex chromosome.

* The X sex chromosome is larger than the Y sex chromosome.

* '''Females''' have XX chromosomes.  All oocytes contain one X chromosome, they are the '''homogametic''' sex.

* '''Females''' have '''XX''' chromosomes.  All oocytes contain one X chromosome, they are the '''homogametic''' sex.

* '''Males''' have XY chromosomes.  Spermatozoa form two distinct populations, one containing X chromosomes and one containing Y chromosomes.  They are the '''heterogametic''' sex.

* '''Males''' have '''XY''' chromosomes.  Spermatozoa form two distinct populations, one containing X chromosomes and one containing Y chromosomes.  They are the '''heterogametic''' sex.

 

* The '''Y''' chromosome is required to '''initiate male development'''.

* The '''Y''' chromosome is required to '''initiate male development'''.

* In absence of the Y chromosome, female gonads (Ovaries) will develop.

* In absence of the Y chromosome, female gonads (Ovaries) will develop.

* The prime male determining gene is '''SRY''' (sex determining region of the Y chromosome).  SRY is a very small piece of DNA that acts as a molecular switch to regulate structural genes and autosomal chromosomes

* The prime male determining gene is '''SRY''' (sex determining region of the Y chromosome).  * SRY is a very small piece of DNA that acts as a molecular switch to regulate structural genes and autosomal chromosomes, determining if and when they are to be activated.

* The presence of SRY alone is sufficient to ensure development of male gonads (Testes).

* The presence of SRY alone is sufficient to ensure development of male gonads (Testes).

== Internal Genetalia ==

== Internal Genetalia ==