Sexual Differentiation - Anatomy & Physiology
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Genetic Sex
- Established at the time of fertilisation.
- 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.
- 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.
- The Y chromosome is required to initiate male development.
- 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 presence of SRY alone is sufficient to ensure development of male gonads (Testes).