Germ Cell and Sex

£»Mammalian sex determination : SRY on the Y chromosome

£»Drosophila sex determination : The number of X chromosome

1. Promoter: The twofold higher level of nimerator proteins activates the Sxl by binding to sites in the Pe; at about syncitial blastoderm formation.

2. Sex-lethal gene: Early Sxl expression(female) or not(male).

3. Autoregulatory loop: Later Sxl mRNA productively spliced by early Sxl proteins(female) and thus activates a series of genes determine the sexual state and produce the sexual phenotypes; at the cellular blastoderm stage.

4. Transformer gene: Controlled by Sxl, leads to the female form of the dsx protein being made.

£»Germ cell sex determination: mouse by cell signals

Germ cell sex determination: Drosophila by genetic constitution (autosomous)

£»Dorsage compensation: To ensure the the level of expression of genes carried on the X chromosome is the same in both sexes.

Mammals: Inactivating center of inactivated X chromosome contains Xist, producing a non-coding RNA that coat the inactivating X chromosome.

Drosophila: When Sxl in male is off, the msl is on and thus transcription of the X chromosome in male is double.

£»Germ cell developement

Germ plasm: A special cytoplasm that specify the germ cells.

Spermatogenesis: Germ cells in the embryonic testis become arrested at G1 phase of mitosis. The formation of sperms will carry on in the sexually mature animal.

Oogenesis: The primary oocytes become arrested in the prophase of the first division of meiosis.

£»Fertilization

 

Egg

 

Sperm and its strategy

 

Cumulus cells enbadded in hyaluronic acid.

 

Hyaluronidase on the surface of head.

 

Zona pellucida: A layer of glycoproteins ZP family(1~3)
 

Membrane

 

Acrosomal reaction:
* beta1,4-galactosyltransferase binds to ZP3
£»beta-N-acetylglucosaminidase breaks down the oligosaccharide side chains on the glycoproteins.
£»Acrosin: Glycoprotein protease.
£»Fertilin: membrane protein that is involved in the fusion of sperm and egg membranes, binds an intergrin-like receptor.

 

Cortical granule

 

Cortical reaction triggering: Contents released, leading to the formation of fertilization membrane and hyaline layer.