Meiosis Flashcards
What is the purpose of meiosis
To form 4 genetically unique haploid gametes for sexual reproduction
What happens to number of chromosomes during meiosis
It’s halved - diploid (2n) to haploid (n)
What is crossing over and when does it occur
Homologous chromosomes exchange genetic material in prophase 1
This increases genetic variation
What happens in metaphase I
Homologous pairs line up on equator of cell and independent assortment takes place
Spindle fibres attach to centromeres
What is independent assortment
The random orientation of homologous chromosomes on equator during metaphase I
What happens during prophase I
Chromosomes condense
Homologous chromosomes pair up (bivalent) ready to go to equator
Crossing over
Nuclear envelope breaks down
Spindle forms
Anaphase I
Homologous chromosomes are pulled apart to opposite poles
Sister chromatids stay together
Telophase I
Chromosomes reach poles
Nuclear envelope may reform
Then cytokinesis
Prophase 2
Chromosomes condense again
New spindle forms
Metaphase 2
Individual chromosomes line up on the equator (not in pairs anymore bc they’ve already been divided)
Spindle fibres attach to centromeres
Anaphase 2
Sister chromatids pulled apart to opposite poles
Telophase 2
Chromatids uncoil
Nuclear envelope reform
Cytokinesis occurs and 4 genetically unique haploid cells
