Question

1.  DISCUSS THE ROLE OF EGF(Epidermal Growth Factor) IN STEROIDOGENESIS

2.  DISCUSS THE ROLE OF StAR IN STEROIDOGENESIS

3. Name 5 differences between male and female meiosis

Answer 1

1.induction of P450scc mRNA and progesterone secretion by FSH is attenuated or blocked by EGF. EGFR signaling is critical for normal gonadotropin-induced steroidogenesis in both male and female gonads.steroids promoted oocyte maturation in several ovarian follicle models, doing so by signaling through classical steroid receptors.inhibition of metalloproteinase-mediated cleavage of membrane-bound EGF moieties abrogated LH-induced steroidogenesis in ovarian follicles, indicating that LH receptor signaling activates the EGFR by different mechanisms

2.Cholestrol gets transferred from outer mitochondrial membrane to inner via clevage catalyze by cytochrome p450 essential step in steroid biosynthesis. Certain proteins such as sterol carrier protein , steroidogenic activator polypeptide , peripheral benzodiazepine and steroidogenic acute regulatory protein(StAR) facilitate transfer of lipophilic cholestrol through aqueous phase present between membranes.

3.meiosis in males -   

1.It is a continuous process which starts from puberty and remains throughout life. The process results into production of millions of spermatozoa daily.

2. occurs at Seminiferous tubules of the testicles

3.no. of haploid cells -Equal number of haploid cells(4 gametes

4 symmetric cell division

5. completed in days or weeks.

meiosis in females

1.This process may take over 40 years from start to finish. Only a few oocytes reaches upto the final stages, as most of them are lost before birth.

2. occurs in Oogonia (ovary)

3.no. of haploid cells- A single enlarged haploid cell

4.assymetric cell division

5. delayed for months or years.