Meiosis Cell division that makes 4 genetically different daughter cells Occurs in sex cells (sperm & eggs) called gametes Chromosome Number per cell is cut in half, which is called the haploid number

Meiosis Stages 2 stages Meiosis I (ALMOST LIKE MITOSIS) Meiosis II (JUST LIKE MITOSIS)

Three special things that happen in Meiosis Synapsis (Prophase I) Crossing Over (Prophase I) Reduction/Division

1. Synapsis Happens during Prophase 1 Synapsis: each pair of homologous chromosomes line up gene by gene Homologous chromosomes are chromosomes that have the same genes in the same place

Homologous Chromosomes

2.Crossing Over Crossing-over chromosomes exchange genetic information.

It is because of crossing over, you don’t look exactly like your mom or dad and we have greater genetic diversity

3. Reduction Division Meiosis goes through two divisions Meiosis REDUCES the number of chromosomes in each cell The result is 4 GENETICALLY DIFFERENT HAPLOID cells. That means 4 cells, with half the number of chromosomes that are different from each other. HAPLOID MEANS HALF

92 46 46 23 23 23 23

Either 4 sperm are made OR 1 egg and 3 polar bodies Spermatogenesis is the making of sperm Oogenesis is the making of eggs * You start with the diploid number (92/46) and you end with the haploid number (23)

Mitosis vs Meiosis Mitosis Meiosis Results in 2 Diploid Cells (2n) 4 Haploid Cells (n) Cells are Genetically Identical Genetically Different Process Cell division Reduction division Occurs in Somatic (Body) Cells Sex Cells