Meiosis (produces sex cells)

Meiosis Genetics requires that organisms inherit a single copy of each gene from each parent Produces cells with half the number of normal chromosomes (1N or haploid) Produces sex cells or gametes 23 23

Two Types of Gametes 1. Sperm Made in males testes Produced puberty death Made every day 100 million sperm/day

Two Types of Gametes 2. Egg or Ova Made in females ovaries Starts 3rd month fetal development ~ 600,000 Release 1/month from puberty menopause ~ Use 600

Plant Reproduction-Yes, Sexual Pollen-sperm Ovules-eggs

Gamete Production =Gametogenesis Spermatogenesis: Production of sperm cells Oogenesis: Production of egg cell (ova)

Meiosis Working WITH Mitosis to Form YOU!!!!! EGG 46 23 23 SPERM Mitosis = Body Cells Gametes made during Meiosis Zygote 23 Dad’s Chromosomes correspond with Mom’s 23 Contains ½ chromosomes from Mom ½ from Dad

Terminology/Vocab Mitosis Meiosis Diploid Monoploid/Haploid 2N 1N or N 46 Full Set of Chromosomes Somatic Cells (Body) Zygote Meiosis Monoploid/Haploid 1N or N 23 ½ # Chromosomes Sex Cells Gametes

Meiosis 1 Interphase 1 G1 = Cell grows and matures S= DNA REPLICATION Occurs in testicle or ovary cells G1 = Cell grows and matures S= DNA REPLICATION G2= Cell makes new organelles

Meiosis 1 Prophase 1 Nucleus and nucleolus disappear Chromatin  chromosomes Chromosomes pair up into homologous pairs Crossing over/genetic recombination may occur which produces gene combinations Spindle fibers appear

M M M D D D Homologous Pairs -have the same structure -1 from Mom, 1 from Dad -Chromosome pairs 1-22 are autosomes -Sex chromosomes X and Y, determine gender in mammals (pair #23) D D D

1 2 3 4 Dad Mom Homologous pairs/chromosomes homologous chromosomes sister chromatids Homologous pairs/chromosomes Forms a Tetrad (4 Sister Chromatids)

Genetic material from the homologous chromosomes is randomly swapped

Meiosis 1 Metaphase 1 Homologous pairs line up at equator

Meiosis 1 Anaphase 1 Homologous pairs separate and move to poles

Meiosis 1 Telophase 1 & Cytokinesis Nucleus and nucleolus reappear Chromosomes  chromatin Spindle fibers fold up  centrioles Cytokinesis = cytoplasm splits

Meiosis 2 SAME AS MITOSIS EXCEPT… **DNA does NOT replicate** Interphase 2 Resting period

Meiosis 2 Prophase 2 Nucleus disappears Nucleolus disappears Chromatin  chromosomes Spindle fibers appear

Meiosis 2 Metaphase 2 Chromosomes line up at the equator Line up on spindle fibers Centromere holds in place

Meiosis 2 Anaphase 2 Sister chromatids separate and move to poles

Meiosis 2 Telophase 2 & Cytokinesis 2 Nucleus and nucleolus reappear Chromosomes  chromatin Centrioles Cells split 4 cells with 1/2 the number of chromosomes – GENETICALLY DIFFERENT CELLS!!!!!!

BOYS: SPERMATOGENESIS Meiosis 1 Meiosis 2 Males 4 Sperm All Equal in Size 23 Chromosomes Meiosis 1 Meiosis 2

Girls: OOGENESIS Meiosis 1 Meiosis 2 Females 1 Viable Egg 23 Chromosomes 3 Polar Bodies (Duds) Meiosis 1 Meiosis 2