Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 13 Meiosis and Sexual Life Cycles

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Asexual vs. Sexual Reproduction Asexual reproduction – One parent  one genetically identical offspring Figure 13.2 Parent Bud 0.5 mm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Asexual vs. Sexual Reproduction Sexual reproduction – Two parents  one unique offspring Figure 13.1

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 13.1: Genome Chromosomes DNA molecule and proteins (Chromatin) Genes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings MEIOSIS Somatic (body) cells – Chromosomes are matched in homologous pairs Ex: human cells have 46 chromosomes = 23 pairs of homologous chromosomes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Every chromosome has a match! = homologous pair Figure 8.12

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Every chromosome has a match! = homologous pair Figure 8.12 Why do we have 2 of each chromosome?

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Somatic Cells vs. Gametes – Somatic Cells 2 sets of chromosomes = Diploid (2n) (n = number of chromosomes in a single set)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Somatic Cells vs. Gametes – Somatic Cells 2 sets of chromosomes = Diploid (2n) (n = number of chromosomes in a single set) – Gametes (eggs and sperm) 1 set of chromosomes = Haploid (n)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Somatic cells = diploid cell An organism’s diploid cell has two sets of each of each chromosome 20 from Mom; 20 from Dad What is the diploid number of chromosomes in each of this organism’s somatic cells?

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Somatic cells = diploid cell An organism’s diploid cell has two sets of each of each chromosome 20 from Mom; 20 from Dad What is the diploid number of chromosomes in each of this organism’s somatic cells? 2n = 40

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CHROMOSOME NUMBER AND STRUCTURE 8.19 A karyotype ordered arrangement of a cell’s chromosomes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Human Kayotype- 22 pairs of autosomes, 1 pair sex chromosomes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings chromosomes condensed A B C D -Sister chromatids -Nonsister chromatids -Homologous pair -Centromere

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Somatic cells vs. Gametes Diploid vs. Haploid 2n vs. n

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Somatic cells vs. Gametes Diploid vs. Haploid 2n vs. n How, when, where and why are haploid cells generated?

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.13 How are haploid gametes produced? = MEIOSIS!

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview of Meiosis- 2 cell divisions Diploid cell 2 Haploid cells 4 Haploid cells Separate homologues Separate sister chromatids Diploid cell

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview of Meiosis- 2 cell divisions Diploid 2n 2 Haploid 1n 4 Haploid 1n Separate homologues Separate sister chromatids (n = Chromosome #) Diploid 2n

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Interphase and meiosis I Interphase 

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Interphase and Meiosis I Interphase  Prophase I 1. Synapsis  Homolouges pair = Tetrads 2. Non-sisters cross over = Chiasmata

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Meiosis I Metaphase I  -Tetrads line up at center of cell

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Meiosis I Metaphase I  Anaphase I  -Homologous chromosomes separate

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Meiosis I Metaphase I  Anaphase I  Telophase I

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Review: Interphase and meiosis I Interphase  prophase I  metaphase I  anaphase I  telophaseI Figure 13.8

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Telophase I and cytokinesis  Prophase II -Spindles form in each cell

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Meiosis II Metaphase II  - Sister chromatids line up in center of cell

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Meiosis II Metaphase II  Anaphase II - Sister chromatids separate

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Meiosis II Metaphase II  Anaphase II  Telophase II - 4 Haploid cells

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Telophase I, cytokinesis, and meiosis II

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview of Meiosis Diploid 2n 2 Haploid 1n 4 Haploid 1n Separate homologues Separate sister chromatids n = Chromosome # Diploid 2n

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Meiosis vs. Mitosis 3 events distinguish Meiosis from Mitosis:

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Meiosis vs. Mitosis #1. Meiosis = Homologous chromosomes pair and exchange genetic information - Tetrads - Synapsis - Crossing over (chiasmata)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Meiosis vs. Mitosis #2 Meiosis= Paired homologous chromosomes (tetrads) are positioned on the metaphase plate

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Meiosis vs. Mitosis #3 Anaphase I of Meiosis = homologous pairs move toward opposite poles of the cell

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Meiosis vs. Mitosis #3 Anaphase I of meiosis = homologous pairs move toward opposite poles of the cell Anaphase II of meiosis = sister chromatids separate

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 8.15 Review: A comparison of mitosis and meiosis Homologues pair Homologues split Sister Chromatids split Homologues do not pair

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 13.4: How does Meiosis produce Genetic Variation?

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 13.4: How does Meiosis produce Genetic variation? = Behavior of chromosomes during meiosis: 1.Crossing over 2.Independent assortment = Fertilization: 3. Random fertilization

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 1. Crossing Over - Produces recombinant chromosomes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2. Independent Assortment of Chromosomes Homologous orient randomly at metaphase I of meiosis

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2. Independent Assortment of Chromosomes Homologous orient randomly at metaphase I of meiosis

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 3. Random Fertilization The fusion of gametes – Can produce a zygote with about 64 trillion diploid combinations!!!

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ch. 13 Asexual vs. Sexual reproduction Homologous Chromosomes Somatic cells= Diploid (2n) Gametes= Haploid (1n)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Review! Ch. 13: Meiosis Diploid cell  4 Haploid cells (gametes) Major events? – Prophase I, Anaphase I, Anaphase II Meiosis vs. Mitosis? How does Meiosis produce variation?