Meiosis

0.5 mm Parent Bud (a) Hydra (b) Redwoods Figure 13.2 Figure 13.2 Asexual reproduction in two multicellular organisms. (a) Hydra (b) Redwoods

Chromosome, consisting of two sister chromatids Figure 12.7a G2 of Interphase Prophase Prometaphase Centrosomes (with centriole pairs) Fragments of nuclear envelope Chromatin (duplicated) Early mitotic spindle Aster Nonkinetochore microtubules Centromere Figure 12.7 Exploring: Mitosis in an Animal Cell Plasma membrane Nucleolus Kinetochore Kinetochore microtubule Chromosome, consisting of two sister chromatids Nuclear envelope

Metaphase Anaphase Telophase and Cytokinesis Metaphase plate Figure 12.7b Metaphase Anaphase Telophase and Cytokinesis Metaphase plate Cleavage furrow Nucleolus forming Figure 12.7 Exploring: Mitosis in an Animal Cell Nuclear envelope forming Spindle Centrosome at one spindle pole Daughter chromosomes

Figure 13.3a Figure 13.3 Research Method: Preparing a Karyotype

Pair of homologous duplicated chromosomes Figure 13.3b 5 m Pair of homologous duplicated chromosomes Centromere Sister chromatids Figure 13.3 Research Method: Preparing a Karyotype Metaphase chromosome

Figure 13.3c 5 m Figure 13.3 Research Method: Preparing a Karyotype

Maternal set of chromosomes (n  3) Figure 13.4 Key Key Maternal set of chromosomes (n  3) 2n  6 Paternal set of chromosomes (n  3) Sister chromatids of one duplicated chromosome Centromere Figure 13.4 Describing chromosomes. Two nonsister chromatids in a homologous pair Pair of homologous chromosomes (one from each set)

Diploid multicellular organism Mitosis Figure 13.6a Key Haploid (n) Diploid (2n) n Gametes n n MEIOSIS FERTILIZATION Zygote 2n 2n Figure 13.6 Three types of sexual life cycles. Diploid multicellular organism Mitosis (a) Animals

Haploid multi- cellular organism (gametophyte) Figure 13.6b Key Haploid (n) Diploid (2n) Haploid multi- cellular organism (gametophyte) Mitosis n Mitosis n n n n Spores Gametes MEIOSIS FERTILIZATION Figure 13.6 Three types of sexual life cycles. 2n Diploid multicellular organism (sporophyte) 2n Zygote Mitosis (b) Plants and some algae

Haploid unicellular or multicellular organism Figure 13.6c Key Haploid (n) Diploid (2n) Haploid unicellular or multicellular organism Mitosis n Mitosis n n n n Gametes Figure 13.6 Three types of sexual life cycles. MEIOSIS FERTILIZATION 2n Zygote (c) Most fungi and some protists

Figure 13.6 Key Haploid (n) Haploid multi- cellular organism (gametophyte) Haploid unicellular or multicellular organism Diploid (2n) n Gametes n n Mitosis n Mitosis Mitosis n Mitosis n n n n n MEIOSIS FERTILIZATION Spores n n Gametes n Gametes MEIOSIS FERTILIZATION Zygote MEIOSIS FERTILIZATION 2n 2n 2n Diploid multicellular organism (sporophyte) 2n Zygote Diploid multicellular organism 2n Figure 13.6 Three types of sexual life cycles. Mitosis Mitosis Zygote (a) Animals (b) Plants and some algae (c) Most fungi and some protists

Interphase Meiosis I Meiosis II Figure 13.7-3 Interphase Pair of homologous chromosomes in diploid parent cell Duplicated pair of homologous chromosomes Chromosomes duplicate Sister chromatids Diploid cell with duplicated chromosomes Meiosis I 1 Homologous chromosomes separate Figure 13.7 Overview of meiosis: how meiosis reduces chromosome number. Haploid cells with duplicated chromosomes Meiosis II 2 Sister chromatids separate Haploid cells with unduplicated chromosomes

Telophase I and Cytokinesis Figure 13.8a Telophase I and Cytokinesis Prophase I Metaphase I Anaphase I Centrosome (with centriole pair) Sister chromatids remain attached Sister chromatids Chiasmata Centromere (with kinetochore) Spindle Metaphase plate Cleavage furrow Homologous chromosomes separate Homologous chromosomes Fragments of nuclear envelope Figure 13.8 Exploring: Meiosis in an Animal Cell Microtubule attached to kinetochore Each pair of homologous chromosomes separates. Two haploid cells form; each chromosome still consists of two sister chromatids. Duplicated homologous chromosomes (red and blue) pair and exchange segments; 2n  6 in this example. Chromosomes line up by homologous pairs.

Telophase II and Cytokinesis Figure 13.8b Telophase II and Cytokinesis Prophase II Metaphase II Anaphase II During another round of cell division, the sister chromatids finally separate; four haploid daughter cells result, containing unduplicated chromosomes. Sister chromatids separate Haploid daughter cells forming Figure 13.8 Exploring: Meiosis in an Animal Cell

Secondary spermatocytes Secondary oocyte Figure 46.UN01 Human gametogenesis Spermatogenesis Oogenesis Primary spermatocyte Primary oocyte 2n 2n n Polar body Secondary spermatocytes Secondary oocyte n n n n n n n Spermatids Sperm n n n n Figure 46.UN01 Summary figure, Concept 46.3 n Polar body n Fertilized egg

Chromosome duplication Chromosome duplication Duplicated chromosome Figure 13.9a MITOSIS MEIOSIS Parent cell Chiasma MEIOSIS I Prophase Prophase I Chromosome duplication Chromosome duplication Duplicated chromosome Homologous chromosome pair 2n  6 Metaphase Metaphase I Anaphase Telophase Anaphase I Telophase I Figure 13.9 A comparison of mitosis and meiosis in diploid cells. Daughter cells of meiosis I Haploid n  3 2n 2n MEIOSIS II Daughter cells of mitosis n n n n Daughter cells of meiosis II

Figure 13.9 A comparison of mitosis and meiosis in diploid cells. Figure 13.9b SUMMARY Property Mitosis Meiosis DNA replication Number of divisions Synapsis of homologous chromosomes Number of daughter cells and genetic composition Figure 13.9 A comparison of mitosis and meiosis in diploid cells. Role in the animal body

Two equally probable arrangements of chromosomes at metaphase I Figure 13.10-1 Possibility 1 Possibility 2 Two equally probable arrangements of chromosomes at metaphase I Figure 13.10 The independent assortment of homologous chromosomes in meiosis.

Two equally probable arrangements of chromosomes at metaphase I Figure 13.10-2 Possibility 1 Possibility 2 Two equally probable arrangements of chromosomes at metaphase I Metaphase II Figure 13.10 The independent assortment of homologous chromosomes in meiosis.

Two equally probable arrangements of chromosomes at metaphase I Figure 13.10-3 Possibility 1 Possibility 2 Two equally probable arrangements of chromosomes at metaphase I Metaphase II Figure 13.10 The independent assortment of homologous chromosomes in meiosis. Daughter cells Combination 1 Combination 2 Combination 3 Combination 4

Nonsister chromatids held together during synapsis Figure 13.11-1 Prophase I of meiosis Nonsister chromatids held together during synapsis Pair of homologs Figure 13.11 The results of crossing over during meiosis.

Nonsister chromatids held together during synapsis Figure 13.11-2 Prophase I of meiosis Nonsister chromatids held together during synapsis Pair of homologs Chiasma Centromere TEM Figure 13.11 The results of crossing over during meiosis.

Nonsister chromatids held together during synapsis Figure 13.11-3 Prophase I of meiosis Nonsister chromatids held together during synapsis Pair of homologs Chiasma Centromere TEM Anaphase I Figure 13.11 The results of crossing over during meiosis.

Nonsister chromatids held together during synapsis Figure 13.11-4 Prophase I of meiosis Nonsister chromatids held together during synapsis Pair of homologs Chiasma Centromere TEM Anaphase I Figure 13.11 The results of crossing over during meiosis. Anaphase II

Nonsister chromatids held together during synapsis Figure 13.11-5 Prophase I of meiosis Nonsister chromatids held together during synapsis Pair of homologs Chiasma Centromere TEM Anaphase I Figure 13.11 The results of crossing over during meiosis. Anaphase II Daughter cells Recombinant chromosomes