2.1 Meiosis Introduction
Meiosis occurs in the reproductive organs (called gonads=testes and ovary) to produce the haploid sex cells which have half the genetic chromosomes that the original parental diploid cell had. For every one parental cell that undergoes meiosis 4 daughter cells are produced.
-In ProphaseI of meiosis crossing over occurs which doesn’t occur in mitosis
-Crossing over involves the pairing up of homologous chromosomes (called synapsis ) and the exchange of genes to produce different types of chromosomes
Homologous chromosomes are chromosomes that are identical in length gene sequence position of centromere and banded appearance
-Brothers and Sisters aren’t the same even when they have the right amount of chromosomes from the same parent because they get different genes
factors that increase diversity in sexual organisms
1-crossing over in meiosis I (Prophase I)
2-selection of a mate
3-depends on how the chromosomes line up along the equator in Metaphase
4-which sperm cells meets up with which egg cell
Diversity is important because it enables the population to survive
Meiosis I
=Reduction division
Meiosis II –similar to mitosis
23
23 23
46
23
23
23
PI  MI

AI

TI
PII  MII
AII

TII
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