Heredity Unit Why we are who we are . . . Kinda… We are going to explore the process of meiosis but first we need to learn some background information. We are going to travel back to the cell.

Human Cells Somatic Cells: make up most of your body. Diploid (2n) - contain 2 copies of every chromosome

Human Cells Gametes: are sex cells Animals: sperm and eggs Plants: Pollen and ova Haploid (n) – contain 1 copy of every chromosome

Chromosome Vocabulary Chromosome – entire picture Centromere Sister Chromatids

Chromosome Vocab Homologous chromosomes Two chromosomes that have copies of the same genes

Autosomes: Sex Chromosome: Chromosomes which contain the genes that do not code for the sex of an organism Autosomes: Sex Chromosome: code for the sexual development of an organism

Review We need to have another process that makes cells that are haploid because

Reason we need another process + 46 46 Eeekk! I’m a mutant! 92

Solution

The result of Meiosis + 23 23 Gee it’s nice to be normal! 46

Meiosis Two Stages: Meiosis I Meiosis II Occurs after DNA has been replicated Divides homologous chromosomes (remember we have 2 copies of every chromosome) Concludes with haploid cells with duplicated chromosomes Meiosis II DNA is not replicated Divides sister chromatids Ends with haploid cell(s) with single chromosome

Meiosis I

Crossing Over Goal: increased genetic variation

Meiosis II

The final results - Gametogenesis