1. Meiosis Flashcards
Define meiosis.
Type of cell division where a parent cell divides to create 4 genetically different haploid cells.
What are the cells called that divide by meiosis?
Diploid to start with.
BUT.
The cells that are formed by meis - chromosome numbers half.
What is the difference between meiosis in humans and meiosis in insects/plants?
Meiosis in humans/mammals produces gametes directly.
BUT.
Meiosis in plants/insects it produces haploid cells which later divide by mitosis to become gametes.
Why is meiosis important?
Because it ensures that all organisms produced via sexual reproduction contain the correct number of chromosomes as you would get double the number of chromosomes when the gametes fuse.
STEP ONE of meiosis.
Before meiosis starts, DNA unravels and replicated so there are 2 copies of each chromosome called chromatids.
STEP TWO of meiosis.
DNA condenses forming double-armed chromosome, each made from 2 sister chromatids.
Chromatids joined in middle by centromere.
STEP THREE of meiosis.
Meiosis I (first division) Chromosomes arrange themselves into homogolous pairs.
STEP FOUR of meiosis.
Homologous pairs are separated halving chromosome number.
STEP FIVE of meiosis.
Meiosis II (second division) Pairs of sister chromatids that make up each chromsome are separated. Centromere divided.
STEP SIX of meiosis.
4 haploid cells genetically different each other are produced.
What separates in first division.
Homologous pairs.
What separates in second divison.
Chromatids.
