B. Genetic Sex Flashcards
What are two methods “lower animals” with viviparity use for sex determination?
1) Environmental cues (constant temperature).
2) Estrogens (high levels).
What method do most mammals use for chromosomal sex determination?
Dominant Y, single pair method.
What is the genetic sex of a female?
XX, chromosomally homologous, homogametic.
What is the genetic sex of a male?
XY, chromosomally heterologous, heterogametic.
What genetic sex occurs in the absence of a Y chromosome?
Female.
What genetic sex occurs in the presence of a single Y chromosome, regardless of how many X chromosomes?
Male.
What is TDFy?
The testis-determining factor that must be present on the Y chromosome.
What does SRY stand for?
It stands for the sex-determining region Y chromosome.
Where on the Y chromosome was the TDF found?
It was found on the region just proximal to the pseudoautosomal region on the short arm of the Y chromosome.
Explain what the SRY gene does.
It encodes for the protein SRY. This protein is then transported to the nucleus where it binds to DNA and causes a bend. This releases transcription factors.
Where is the SRY expressed?
In urogenital ridge prior to gonadal differentiation.
What is SRY’s expression independent of?
The presence of primordial germ cells.
What are four other functions of the Y chromosome?
1) Important for spermatogenesis.
2) Regulates (increases) height).
3) Cardiac traits (blood pressure and cholesterol metabolism).
4) “Genetic junk”.
