body cell of mammals =
diploid - has 2 copies of each
chromosome in its nucleus -
one from female + one from
male
gametes are haploid - 1 copy of each
chromosome - combine=diploid
meiosis = 2 divisions
1. starts the same way as mitosis - DNA replicates -
curls up into double armed chromsomes
2. after replication - chromosomes arrange
themselves into pairs - humans = 23pairs of
chromosome = 46 altogether
chromosomes in a pair contain info about the same features
3. 1st division the pairs split up - chromosomes in
each pair move to opposite poles. in each of two new
cells there are no pairs- one of each of the 23
different types- each new cell = mixture of mum +
dads chromosomes- only half the usual number of
chromosomes
4. 2nd division = each chromosome splits in half and one arm ends up in each new cell.