Meiosis, Fertiliasation, and Infertility Flashcards
What’s meiosis
Separation of homologous chromosomes
Then seperate in of sister chromatids
(From producing haploid gametes to then introducing genetic diversity via crossing over and assortment )
How many chromosomes in a human diploid somatic cell?
23 pairs of Chromosomes (22 autosomal pairs and 1 sexual pair)
46 in total (23 maternal and 23 paternal)
How many cross overs happen between each pair of human chromatids per meiosis cycle?
2-3 crossovers on average
Meiosis is regulated differently in males and females, how?
In spermatogenosis, sperm lands when you hit puberty and one parent cell produces 4 sperm cells
Oogenesis only one oocyte formed from a parent cell and other three degenerate and this starts as soon as you’re born maturation continues after puberty
What is aneuploidy?
And what happens when autosomal chromosomes go wrong?
Failure in chromosome separation in Meiosis
Down syndrome
Oocytes and sperm have different error rates in meiosis, what are some of them?
20% of oocytes are aneuploid compared to 3-4% of sperm
This 25% human foetus are aneuploid
But due to loads of mitotic divisions genetic mutations more likely before mature sperm forms
Sperm capacitation facts
-Soern cannot fertilise oocytes when newly ejaculated
-Process of capacitation takes 5-7 hours
-Capacitated sperms are more active
-capacitation occurs at the uterus and oviducts and facilitated by female substances
What is the aim of capacitation?
To increase motility of the sperm flagellum and allow sperm to undergo the acrosome reaction
-By changes in glycoproteins lipids and ion channels in PM
-Lowering resting potential
-uncover surface receptors to bind to egg (the zona pellucida)
What is the acrosome reaction?
Basically where sperm binds to zona pellicuda and releases acrosomal vesicle to get into egg cytoplasm
NB- when one sperm enters egg cortical granule release enzyme altering zona structure and not allowing anymore sperm
