Chapter 13 Meiosis and Sexual Life Cycles PowerPoint Lectures for Biology Eighth Edition Neil Campbell and Jane Reece Fig 13 3 APPLICATION TECHNIQUE 5 m Pair of homologous replicated chromosomes Centromere Sister chromatids Metaphase chromosome In a cell in which DNA synthesis has occurred All the chromosomes are duplicated and thus each consists of two identical sister chromatids Key Maternal set of chromosomes n 3 2n 6 Paternal set of chromosomes n 3 Two sister chromatids of one replicated chromosome Centromere Figure 13 4 Two nonsister chromatids in a homologous pair Pair of homologous chromosomes one from each set Fig 13 5 Key Haploid gametes n 23 Haploid n Egg n Diploid 2n Sperm n FERTILIZATION MEIOSIS Ovary Testis Diploid zygote 2n 46 Mitosis and development Multicellular diploid adults 2n 46 Fig 13 6a The Variety of Sexual Life Cycles Animals Key Haploid n Diploid 2n n Gametes n n MEIOSIS 2n Diploid multicellular organism a Animals FERTILIZATION Zygote 2n Mitosis The Variety of Sexual Life Cycles Plants Key Haploid n Haploid multicellular organism gametophyte Diploid 2n Mitosis n Mitosis n n n n Spores Gametes MEIOSIS FERTILIZATION 2n Diploid multicellular organism sporophyte 2n Zygote Mitosis b Plants and some algae Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Fig 13 6c Key Haploid n Haploid unicellular or multicellular organism Diploid 2n Mitosis Mitosis n n n n Gametes MEIOSIS FERTILIZATION 2n Zygote c Most fungi and some protists n Fig 13 7 3 Interphase Homologous pair of chromosomes in diploid parent cell Chromosomes replicate Homologous pair of replicated chromosomes Sister chromatids Diploid cell with replicated chromosomes Meiosis I 1 Homologous chromosomes separate Haploid cells with replicated chromosomes Meiosis II 2 Sister chromatids separate Haploid cells with unreplicated chromosomes Fig 13 8a Prophase I Metaphase I Centrosome with centriole pair Sister chromatids Chiasmata Spindle Centromere with kinetochore Sister chromatids remain attached Metaphase plate Homologous chromosomes separate Homologous chromosomes Fragments of nuclear envelope Telophase I and Cytokinesis Anaphase I Microtubule attached to kinetochore Cleavage furrow Fig 13 8d Prophase II Metaphase II Anaphase II Telophase II and Cytokinesis Sister chromatids separate Haploid daughter cells forming Fig 13 9 MITOSIS MEIOSIS Parent cell Chromosome replication Prophase Chiasma Chromosome replication Prophase I Homologous chromosome pair 2n 6 Replicated chromosome MEIOSIS I Metaphase Metaphase I Anaphase Telophase Anaphase I Telophase I Haploid n 3 Daughter cells of meiosis I 2n MEIOSIS II 2n Daughter cells of mitosis n n n n Daughter cells of meiosis II SUMMARY Property Mitosis Meiosis DNA replication Occurs during interphase before mitosis begins Occurs during interphase before meiosis I begins Number of divisions One including prophase metaphase anahase and telophase Two each including prophase metaphase anaphase and telophase Synapsis of homologous chromosomes Does not occur Occurs during prophase I along with crossing over between nonsister chromatids resulting chiasmata hold pairs together due to sister chromatid cohesion Number of daughter cells and genetic composition Two each diploid 2n and genetically identical to the parent cell Four each haploid n containing half as many chromosomes as the parent cell genetically different from the parent cell and from each other Role in the animal body Enables multicellular adult to arise from zygote produces cells for growth repair and in some species asexual reproduction Produces gametes reduces number of chromosomes by half and introduces genetic variability amoung the gametes Fig 13 11 3 Possibility 2 Possibility 1 Two equally probable arrangements of chromosomes at metaphase I Metaphase II Daughter cells Combination 1 Combination 2 Combination 3 Combination 4 Fig 13 12 5 Prophase I of meiosis Pair of homologs Nonsister chromatids held together during synapsis Chiasma Centromere TEM Anaphase I Anaphase II Daughter cells Recombinant chromosomes You should now be able to 1 Distinguish between the following terms somatic cell and gamete autosome and sex chromosomes haploid and diploid 2 Describe the events that characterize each phase of meiosis 3 Describe three events that occur during meiosis I but not mitosis 4 Name and explain the three events that contribute to genetic variation in sexually reproducing organisms Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings
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