Meiosis summary

#Biology


Meiosis
One cell gives rise to 4 cells with half the amount of chromosomes in the original cell (4 haploid cells)
Autosome: all cells other than sex cells (code for everything except sex)
Gonosomes: sex cells e.g. sperm in males (code for sex)
In plants Gametes are formed
In animals Gonosomes are formed




Meiosis I
Prophase I
Crossing over occurs (point of crossing over: Chiasma)
Chromosomes split into chromatids
Chromatids exchange genetic information

Metaphase I
Centrioles have reached the poles
Spindle fibers are fully formed (attached to centromere)
Homologous pairs of chromosomes are randomly arranged at the equator of the cell

Annaphase I
Spindle fires contract, pulling chromatids to the the poles of the cell.

Telophase I
Chromosomes reach their poles.
Cytokenisis occurs and sells are split.
Nuclear envelopes forms around the chromosomes.
Two daughter cells are formed, each cell has half the amount of chromosomes.


Meiosis II
Prophase II
No crossing over takes places and spindle fibers begin to form.

Metaphase II
Single row of chromosomes are arranged in a line at the equator of the cell
spindle fibers are fully formed (attached to centromere)

Anaphase II
Sister chromatids are pulled apart and move to the poles of the cell.