Meiosis vs. Mitosis

I. Mitosis vs. Meiosis Mitosis Cell division 46 chromo2 cells, 46 chromo. Each Keeps chromo. # same Found in body cells Most common No genetic variation Meiosis Cell division 46 chromo 4 cells, 23 chromo each Chromo. # cut in half Found in sex/germ cells ONLY Least common Most genetic variation ANIMATION OF COMPARISON ANIMATION 2 OF COMPARISON

II. Chromosomes Karyotypes: Display of chromosomes lined up in homologous pairs Half inherited from male Half from female Used for viewing #, size, shape, and banding patterns of chromosomes

Homologous Chromosomes: matching pair of chromosomes, one inherited from each parent

Body cells/Somatic Cells= “Diploid”or 2N having two sets of chromosomes, body cells Humans 46 chromosomes

Sex cells/Sperm + Egg= “Haploid”or N having one set of chromosomes, sex cells ( gametes) Ex: Humans 23 chromosomes

when haploid sperm and egg meet, combining N chromosomes Fertilization: when haploid sperm and egg meet, combining N chromosomes with N chromosomes = 2N zygote Zygote: fertilized egg, 2N ____ ____ ____ 23 23 46 sperm egg zygote

Diploid vs. Haploid Exercises Drosophilia have a diploid number of 8. What is the haploid? Onions have a haploid number of 8. What is the 2N? A horse’s 2N is 64. What is the 1N? A body cell of an alligator has 32 chromosomes. Is this the diploid or haploid number? 4 16 32 Diploid

II. Meiosis Definition: cell division to produce egg (ovule) or sperm (pollen) Meiosis I & Meiosis II

Oogenesis: Production of Egg Female meiosis in the ovaries Resulting cells: 1 egg, 3 polar bodies Haploid

Spermatogenesis: Production of Sperm Male meiosis in testes Resulting cells: 4 haploid sperm cells Animation spermatogenesis

Meiosis I (PMAT I & C) Prophase I: homologous chromosomes meet up and form tetrads. Crossing over occurs. What is the point of crossing over?

Meiosis II (PMAT II & C) What if Meiosis did not occur?