Gametogenesis Flashcards
(18 cards)
What is gametogenesis?
process by which haploids are formed from diploids or haploids.
process to obtain gametes via meiosis
2 forms of gametogenesis
spermatogenesis
oogenesis
Meiosis involves 1 round of … and 2 rounds of …
chromosomal duplication
nuclear divison
Spermatogenesis takes about … and occurs in the …
70 days
seminiferous tubules
Spermatogenesis process:
1) Diploid cells undergo mitosis and form type A and B cells
2) Type B differentiate into primary spermatocytes
3) Primary spermatocytes undergo meiosis I.
4) In meiosis I homologous chromosomes pair up and exchange genetic material through crossing over. There are now 2 haploid secondary spermatocytes which contain a unique combination of genetic material.
5) the secondary spermatocytes divide into 4 haploid spermatids in meiosis II.
Why do the testicles hang lower in the male body?
spermatogenesis requires a cooler temp
Facts about sperm production
start being produced at puberty (10-16) (lifelong)
produced in large quantities - 200 million a day (to increase fertilisation)
The seminiferous tubules are kept separate…
from the systemic circulation by the blood-testis barrier
What happens after spermatids are formed?
1) Spermiation - they’re released into the lumen of the seminiferous tubules
2) They get transported to the epididymis where they are stored and undergo the final stages of maturation
3) They get released as semen during ejaculation alongside secretions from the prostate.
What is in the secretions from the prostate during ejaculation and why?
seminal vesicles + bulbourethral glands
they help the sperm overcome the environment of of the female reproductive tract.
What is the name of the process that allows the sperm to fertilise the egg?
capacitation
what is oogenesis?
the process by which meiosis leads to the formation of an egg cell
What is fertilisation?
the fusion between the sperm and egg cell to produce a zygote. (initial cell of a foetus)
The process of oogenesis
1) in a developing female embryo
2) Primary oocytes are arrested in prophase I until a female reaches puberty
2) During each month (ovulation) an oocyte resumes meiosis - a secondary oocyte receives the majority of the cytoplasm and polar body forms.
3) the haploid secondary oocyte carries on with meiosis II.
4) Meiosis II is halted at metaphase II until fertilisation (or gets shed)
5) Fertilisation = meiosis II finishes = forms an ootid
6) ootid matures to ovum
7) polar bodies form to discard extra set of chromosomes ensuring the final egg cell is haploid.
When does capacitation occur?
when the sperm swims through the uterus into the oviduct.
`What happens in capacitation?
the membrane over the sperms acrosome is weakened (chemical changes)
enzymes are released from the sperm clearing a path through the zone pellucid
Fusion of the sperm allows for…
the oocyte to mature into an ovum and polar body. (also stops more sperm entry)
what are polar bodies
a structure used to dump genetic material
