L2: Gametogenesis (onaizi) Flashcards
(34 cards)
Incorrect migration of germ cells leads to what?
Congenital anomalies (teratomas)
Gametogenesis is characterized into 4 stages:
- The extraembryonic origin of the germ cells and their migration into the gonads,
- An increase in the number of germ cells by mitosis, (Mitosis ensures a large reservoir for future gametes)
- A reduction in chromosomal number by
meiosis, and - Structural and functional maturation of
the eggs and spermatozoa.
Who developed the chromosomal theory of inheritance?
Sutton and boveri in 1902
Genes in the same chromosome is known as?
Linked genes
Humans have ~_________ genes on 46 chromosomes
35,000
The number of germ cells peak due to mitosis during which months of pregnancy?
2nd-5th month of pregnancy
Name a couple of differences between oocytes and spermatocytes
- 1 primary oocyte gives rise to 4 daughter cells (each 22 plus one X chromosome) bas only one matures while the other 3 polar bodies degenerate,
- however in males all of them mature (two are 22 chromosomes plus 1 X, w il other two are 22 plus one Y)
- Oogonia undergo programmed degeneration called atresia until menopause while spermatogonia maintain the ability to divide until death
Why is there no new formation of primary oocyte after birth?
Bc there is no oogonia at birth
What is a primordial follicle?
A primary oocyte surrounded by a layer of flat epithelial cells
Explain what happens to the oocytes before the girl hits puberty
- At birth all primary oocytes have started PROPHASE of meiosis 1, but do not enter metaphase, they’re arrested at diplotene stage (a part of prophase) until puberty
- Most oocytes become atretic during childhood- only 40,000 are present by puberty and less than 500 will be ovulated
Oocytes that reach maturity late in life have been?
dormant for 40 years or more before ovulation
What is the oocyte size after the girl hits puberty?
Secondary follicle = primary oocyte
When does the primary follicle turn into a secondary follicle?
After puberty
If the egg wasn’t fertilized, the follicle is arrested at what stage?
Meiosis II of metaphase II
How many primary follicles are growing every monthly cycle?
5-15
Explain growth il primordial follicle
When does mitosis and meiosis start in males?
Mitosis is continuous in males and meiosis starts after puberty
Summarize the division of spermatogonia
Summarize the maturation of oogonia
Explain maturation of il sperm appearance
Genetic variability is increased by?
How does chromosomal abnormalities occur?
What are examples of chromosomal disabilities (aneuploidies)?
What is the first haploid cell in male gametogenesis?
Spermatids
