Review

Meiosis Sexual Reproduction

What is meiosis? Animals Process that makes the sperm and egg Plants Process that makes the pollen and ovule

Sexual Reproduction Fertilization Example: The combination of two haploid Cells to create a diploid cell Example: Haploid (n) Sperm or egg Diploid (2n)– Zygote (fertilized egg) Sperm(n) + egg(n) = zygote(2n) N= 23 Chromosomes For Humans only

Fertilization vs Pollination Fertilization (animals) Gamete + Gamete -->Zygote Sperm + Egg --> Zygote n + n --> 2n Haploid + Haploid --> Diploid Pollination (Plants) Pollen + Ovule --> Seed n + n --> 2n

Meiosis

Phases of Meiosis Meiosis I Interphase Prophase I Metaphase I Basically Mitosis, twice…. Meiosis I Interphase Prophase I Metaphase I Anaphase I Telophase I Meiosis II ProphaseII Metaphase II Anaphase II Telophase II

Meiosis

Meiosis 2 gametes combine to form one zygote Meiosis I The cell (2n) splits into 2 cells Each cell is haploid (n) has 23 replicated chromosomes Meiosis II Those 2 cells then split into 4 cells Separating the sister chromatids The 4 resulting cells become egg and sperm [each is haploid (n)] Oogenesis creates eggs Spermatogeneis creates the sperm

Sperm and Egg Creation Spermatogenesis creates 4 sperm Oogenesis creates 1 egg

Genetic Variation Meiosis is IMPORTANT to genetic variation (different types) Crossing- over: Exchange of genetic material between chromosomes, creates new combinations (Prophase I) Independent Assortment : Whichever copy goes into the gamete (egg or sperm) is random (Metaphase I)

Comparison of Mitosis and Meiosis Purpose Growth and Repair Reproduction (genetic variation) # of Divisions 1 2 Parent Cell 2n (diploid) Daughter Cells 2n and Identical to parent 4 n and not identical Type of Cells Produced Somatic Cells Gametes

Review Mitosis or Meiosis? A B Mitosis Meiosis

Ribbit…..ribbit Thanks for listening!!

Meiosis Video Clip http://www.ebaumsworld.com/video/watch/82148080/ http://www.youtube.com/watch?v=uh7c8YbYGqo&feature=related http://www.youtube.com/watch?v=35ncSrJOwME