Meiosis

Mitosis Meiosis Copy of a cell VS. Division in which 4 new cells are made with half of the original DNA New cells are different than the original cell Make gametes: sperm and egg Copy of a cell 46 diploid 46 diploid 46 46 23 23 haploid diploid diploid 23 23 23 23 haploid

Meiosis Animation

I. Meiosis A. Which cells undergo meiosis? 1. Only cells within the testis and the ovaries produce gametes a. Gametes: haploid sperm and egg B. Why meiosis? 1. You only want half (23) the number of chromosomes in each sex cell 2. So…you need to have 2 divisions

Interphase Cell grows DNA replicates

Prophase I Tetrads form: homologous pairs buddy up Crossing Over: parts of the homologous chromosomes switch places * New combination of traits!

Crossing over

Metaphase I Homologous chromosomes line up RANDOMLY Independent assortment New combinations of traits *Different than mitosis!

Independent Assortment

Anaphase I Homologous chromosomes are separated Sister chromatids stay attached *Different than mitosis

Telophase I and Cytokinesis I End up with 2 HAPLOID cells Each cell has one homologous chromosome form the pair 1n 1n

Prophase II

Metaphase II Chromosomes line up along equator *Same as in mitosis

Anaphase II Chromatids are pulled apart *Like in mitosis

Telophase II and Cytokinesis II

Gametes produced: * 4 sperm * 1 egg and 3 polar bodies Gametes