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Figure 13.4 Key Maternal set of 2n = 6 chromosomes (n = 3) Paternal set of chromosomes (n = 3) Sister chromatids of one duplicated chromosome Centromere Two nonsister Pair of homologous chromatids in chromosomes a homologous pair (one from each set)
Figure 13.7-3 Interphase Pair of homologous chromosomes in diploid parent cell Duplicated pair Chromosomes of homologous duplicate chromosomes Sister Diploid cell with chromatids duplicated chromosomes Meiosis I 1 Homologous chromosomes separate Haploid cells with duplicated chromosomes Meiosis II 2 Sister chromatids separate Haploid cells with unduplicated chromosomes
Figure 13.8a Metaphase I Anaphase I Telophase I and Prophase I Cytokinesis Centrosome (with centriole pair) Sister chromatids remain attached Sister Chiasmata Centromere chromatids (with kinetochore) Spindle Metaphase plate Cleavage furrow Homologous Homologous Fragments chromosomes chromosomes of nuclear separate envelope Microtubule Each pair of homologous Two haploid attached to chromosomes separates. cells form; each kinetochore chromosome Duplicated homologous Chromosomes line up still consists chromosomes (red and blue) by homologous pairs. of two sister pair and exchange segments; chromatids. 2n = 6 in this example.
Figure 13.8b Telophase II and Prophase II Metaphase II Anaphase II Cytokinesis During another round of cell division, the sister chromatids finally separate; four haploid daughter cells result, containing unduplicated chromosomes. Sister chromatids Haploid daughter separate cells forming
Figure 13.8 MEIOSIS I: Separates homologous chromosomes MEIOSIS I: Separates sister chromatids Telophase I and Telophase II and Prophase I Metaphase I Anaphase I Prophase II Metaphase II Anaphase II Cytokinesis Cytokinesis Centrosome Sister chromatids (with centriole pair) remain attached Sister Chiasmata Centromere chromatids (with kinetochore) Spindle Metaphase plate During another round of cell division, the sister chromatids finally separate; Cleavage four haploid daughter cells result, containing unduplicated chromosomes. furrow Homologous Sister chromatids Haploid daughter Homologous Fragments chromosomes separate cells forming chromosomes of nuclear separate envelope Microtubule Each pair of homologous Two haploid cells attached to chromosomes separates. form; each chromosome kinetochore still consists of two Chromosomes line up sister chromatids. Duplicated homologous chromosomes (red and blue) by homologous pairs. pair and exchange segments; 2n = 6 in this example.
Figure 13.9 MITOSIS MEIOSIS Parent cell MEIOSIS I Chiasma Prophase Prophase I Chromosome Chromosome Duplicated Homologous duplication duplication chromosome 2n = 6 chromosome pair Metaphase Metaphase I Anaphase Anaphase I Telophase Telophase I Haploid n=3 Daughter cells of meiosis I 2n 2n MEIOSIS II Daughter cells n n n n of mitosis Daughter cells of meiosis II SUMMARY Property Mitosis Meiosis DNA Occurs during interphase before Occurs during interphase before meiosis I begins replication mitosis begins Number of One, including prophase, metaphase, Two, each including prophase, metaphase, anaphase, divisions anaphase, and telophase and telophase Synapsis of Does not occur Occurs during prophase I along with crossing over homologous between nonsister chromatids; resulting chiasmata chromosomes hold pairs together due to sister chromatid cohesion Number of Two, each diploid (2n) and genetically Four, each haploid (n), containing half as many daughter cells identical to the parent cell chromosomes as the parent cell; genetically different and genetic from the parent cell and from each other composition Role in the Enables multicellular adult to arise from Produces gametes; reduces number of chromosomes animal body zygote; produces cells for growth, repair, by half and introduces genetic variability among the and, in some species, asexual reproduction gametes