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

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 13.1 Francis Ford Coppola and his family

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 13.2 The asexual reproduction of a hydra Parent Bud 0.5 mm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 13.2 Hydra Budding Animation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 13.3 Preparing a Karyotype APPLICATION A karyotype is a display of condensed chromosomes arranged in pairs. Karyotyping can be used to screen for abnormal numbers of chromosomes or defective chromosomes associated with certain congenital disorders, such as Down syndrome. TECHNIQUE Karyotypes are prepared from isolated somatic cells, which are treated with a drug to stimulate mitosis and then grown in culture for several days. A slide of cells arrested in metaphase is stained and then viewed with a microscope equipped with a digital camera. A digital photograph of the chromosomes is entered into a computer, and the chromosomes are electronically rearranged into pairs according to size and shape. RESULTS This karyotype shows the chromosomes from a normal human male. The patterns of stained bands help identify specific chromosomes and parts of chromosomes. Although difficult to discern in the karyotype, each metaphase chromosome consists of two, closely attached sister chromatids (see diagram). 5 µm Pair of homologous chromosomes Centromere Sister chromatids

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 13.4 Describing chromosomes Key Maternal set of chromosomes (n = 3) Paternal set of chromosomes (n = 3) 2n = 6 Two sister chromatids of one replicated chromosome Two nonsister chromatids in a homologous pair Pair of homologous chromosomes (one from each set) Centromere

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 13.5 The human life cycle Key Haploid (n) Diploid (2n) Haploid gametes (n = 23) Ovum (n) Sperm Cell (n) MEIOSIS FERTILIZATION Ovary Testis Diploid zygote (2n = 46) Mitosis and development Multicellular diploid adults (2n = 46)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Diploid multicellular organism Key MEIOSIS FERTILIZATION MEIOSIS FERTILIZATION MEIOSIS FERTILIZATION n n n n n n n n n n n n n 2n Zygote Gametes Haploid multicellular organism (gametophyte) Haploid multicellular organism Haploid Diploid Mitosis Spores Gametes Mitosis Gametes Mitosis Zygote Mitosis (a) Animals Diploid multicellular organism (sporophyte) (b) Plants and some algae (c) Most fungi and some protists Figure 13.6 Three types of sexual life cycles

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 13.7 Overview of meiosis: how meiosis reduces chromosome number Interphase Homologous pair of chromosomes in diploid parent cell Chromosomes replicate Homologous pair of replicated chromosomes Sister chromatids Diploid cell with replicated chromosomes 1 2 Homologous chromosomes separate Haploid cells with replicated chromosomes Sister chromatids separate Haploid cells with unreplicated chromosomes Meiosis I Meiosis II

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 13.8 The Meiotic Division of an Animal Cell Centrosomes (with centriole pairs) Sister chromatids Chiasmata Spindle Tetrad Nuclear envelope Chromatin Centromere (with kinetochore) Microtubule attached to kinetochore Tetrads line up Metaphase plate Homologous chromosomes separate Sister chromatids remain attached Pairs of homologous chromosomes split up Chromosomes duplicate Homologous chromosomes (red and blue) pair and exchange segments; 2n = 6 in this example INTERPHASE MEIOSIS I: Separates homologous chromosomes PROPHASE I METAPHASE I ANAPHASE I

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 13.8 The Meiotic Division of an Animal Cell TELOPHASE I AND CYTOKINESIS PROPHASE II METAPHASE II ANAPHASE II TELOPHASE II AND CYTOKINESIS MEIOSIS II: Separates sister chromatids Cleavage furrow Sister chromatids separate Haploid daughter cells forming During another round of cell division, the sister chromatids finally separate; four haploid daughter cells result, containing single chromosomes Two haploid cells form; chromosomes are still double

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 13.9 A comparison of mitosis and meiosis MITOSIS MEIOSIS Prophase Duplicated chromosome (two sister chromatids) Chromosome replication Chromosome replication Parent cell (before chromosome replication) Chiasma (site of crossing over) MEIOSIS I Prophase I Tetrad formed by synapsis of homologous chromosomes Metaphase Chromosomes positioned at the metaphase plate Tetrads positioned at the metaphase plate Metaphase I Anaphase I Telophase I Haploid n = 3 MEIOSIS II Daughter cells of meiosis I Homologues separate during anaphase I; sister chromatids remain together Daughter cells of meiosis II n n nn Sister chromatids separate during anaphase II Anaphase Telophase Sister chromatids separate during anaphase 2n2n2n2n Daughter cells of mitosis 2n = 6

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The independent assortment of homologous chromosomes in meiosis Key Maternal set of chromosomes Paternal set of chromosomes Possibility 1 Two equally probable arrangements of chromosomes at metaphase I Possibility 2 Metaphase II Daughter cells Combination 1 Combination 2Combination 3Combination 4

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The results of crossing over during meiosis Prophase I of meiosis Nonsister chromatids Tetrad Chiasma, site of crossing over Metaphase I Metaphase II Daughter cells Recombinant chromosomes