Gametogenesis fertilization, and non-disjunction

Gametogenesis

Process of forming ova or sperm (gametes) following the steps of mitosis

Oogenesis when does it start and end

Starts in fetal development and arrests until puberty. Recommences, but arrests until fertilization in m2. Menopause in 50s stops process all together.

Spermatogenesis

Daily mitosis -- Starts at puberty and until death.

Oogensis at puberty

1 follicle which contains an ova will be chosen to continue mitosis. It will arrest in M2 until fertilisation

2 cells combine to make what

haploid ova and haploid sperm combine to make diploid zygote.

Unequal divison of cytoplasm

During oogenesis, germ cell divides, producing one ova and 3 polar bodies over the course of mitosis 1 and 2. Only 1 viable ova.

Spermatogensis meiosis

produces 4 viable offspring

non-disjunction

when chromosomes fail to separate during anaphase. Daughter cells will end with with too many (n+1) or too few (n-1) chromosomes.

non-disjunction in meosis

affects all body cells of embryo.

Chromosomal disorders

1. Monosomy (n-1)

2. Trisomy (n+1)

How to diagnose chromosomal disorders

karyotypes -- chromosomes 1-22 are autosomes and #23 are sex chromosomes

sex chromosome combos

xx = women xy = male

Abberation

NOT a non-disjunction. When a peice of a chromosome is either added or deleted during crossing over.

Down syndrome

Extra chromosome #21. Trisomy

Klinefeller

extra x chromosome in male (xxy or xxxxy for example)

Turner syndrom

missing x chromosome in women. monosomy n-1