University:
Swansea University
Course:
PM-133 | Evolutionary and Molecular Genetics
Academic year:

2023
Views:

99

Pages:

3
Author:

Amal J.

Oogenesis in Drosophila Model organism in DB. Meroistic oogenesis → because during the term of oogenesis, the oocyte is in contact with neighboring cells, the neighboring cells provide nourishment to the developing oocyte through cytoplasmic connection. Oogonia: Oosome. Cytoblast (already determines which cell forms the oocyte). Cytoplasmic connection (ring canal). 4 → 8 → 16 cell stage. 16 cell stage: At the 16 cell stage, 2 cells in the 16 cells have cytoplasmic connections. These 2 cells acquire more nutrients from neighboring cells. They have equal fate to become oocyte, but only one becomes an oocyte. Entire 16 cells are covered in a chamber of egg shell called germarium. 15 = Nurse cells. 1 = Oocyte precursor. Cytoplasmic determinants (protein-rich molecules): Fusome (Spectrin rich), which spans the ring canal. Fusome → cells which get more amount of Fusome become the oocyte. Mammals PGC not able to differentiate by itself → gonads determine ♀ or ♂ gametes. Gonads give licensing factors which helps in differentiation into ♀ or ♂. DAZL → Protein in developing gonad that acts as a licensing factor for male and female sex determination. Meiosis initiated by 2 molecules: In females: meiosis starts at fetal stage (5 months) → Blocked at diplotene I. In males: meiosis starts @ puberty. In females, PGC @ gestation → Stra8 protein → Upregulated by Retinoic acid → becomes female. Progression of meiosis. In males: Retinoic acid degraded by Cyp26 → Inhibit Stra8. Inhibits the expression of Stra8. When we experimentally induce Nanos2 in female germ cells → Stra8 inhibited → Male fate. In males, sertoli cells are able to produce Retinoic acid @puberty → Stra8 → Progression of meiosis.