Friday April 2, 1999
Announcements:

Lecture notes:

Determination of female or male phenotype

A gene on the Y chromosome codes for TDF (Testis Determining Factor)

Week 1-7: Undifferentiated structures.

Week 8 (males): TDF turns on production of "inhibitor substance" and fetal androgens.

Inhibitor substance has a local effect to inhibit the Mullerian ducts.

Androgens have a systematic effect to develop the Wolffian ducts into internal genital structures and to masclinize the external genital structures.

The undifferentiated gonad becomes the testis.

Absence of TDF will result in differentiation into female structures.

The Mullerian duct system becomes the female internal genitalia.

In the absence of TDF, Wolffian ducts regress.

The genital swelling becomes the female external genitals.

The gonad becomes and ovary.

This occurs after the 8^th week.

Differentiation

Causes of hermaphroditism

1. Sex chromosomes imbalance (True hermaphroditism) This occurs from a union of male and female zygotes at the morula stage, or from a mitotic mistake early in development.
   
   Genotype is xy/xx, or xy/xo
2. Masculinization of a genetic female.
   
   a. occurs at 8-13 weeks.
   b. from adrenal tumor in fetus (excess androgens) or…
   c. excess maternal androgens
   - from a tumor
   - latrogenic- given hormones for some medical reason.
3. Feminization of genetic males
   
   a. defective testis development.
   b. androgen insensitivity (testicular feminizing syndrome)
4. Pseudohermaphroditism: missing a gene to turn testosterone to dihydrotestosterone in the fetus.