Figure 8.12A

Figure 8.12A Haploid gametes (n 23) Sexual reproduction produces genetically different offspring n Egg cell n Sperm cell Meiosis Fertilization Ovary Testis Diploid zygote (2n 46) 2n Key Mitosis Haploid stage (n) Multicellular diploid adults (2n 46) Diploid stage (2n)

Fig. 8-11

Figure 8.12B How meiosis reduces chromosome number INTERPHASE MEIOSIS I MEIOSIS II Sister chromatids 2 1 3 A pair of homologous chromosomes in a diploid parent cell A pair of duplicated homologous chromosomes

Figure 8.13_left MEIOSISI: Homologous chromosomes separate INTERPHASE: Chromosomes duplicate Prophase I Metaphase I Anaphase I Centrosomes (with centriole pairs) Spindle microtubules attached to a kinetochore Sister chromatids remain attached Sites of crossing over Centrioles Spindle Tetrad Sister chromatids Metaphase plate Chromatin Centromere (with a kinetochore) Nuclear envelope Fragments of the nuclear envelope Homologous chromosomes separate Unique to meiosis, not found in mitosis

Figure 8.13_right MEIOSISII: Sister chromatids separate Telophase II and Cytokinesis Telophase I and Cytokinesis Prophase II Metaphase II Anaphase II Cleavage furrow Haploid daughter cells forming Sister chromatids separate

Figure 8.14 MEIOSISI MITOSIS Parent cell (before chromosome duplication) Site of crossing over Prophase Prophase I Tetrad formed by synapsis of homologous chromosomes Duplicated chromosome (two sister chromatids) Chromosome duplication Chromosome duplication 2n 4 Metaphase I Metaphase Tetrads (homologous pairs) align at the metaphase plate Chromosomes align at the metaphase plate Anaphase I Telophase I Anaphase Telophase Homologous chromosomes separate during anaphase I; sister chromatids remain together Sister chromatids separate during anaphase Haploid n 2 Daughter cells of meiosis I MEIOSISII 2n 2n No further chromosomal duplication; sister chromatids separate during anaphase II Daughter cells of mitosis n n n n Daughter cells of meiosis II

Figure 8.15_s1 Possibility A Possibility B Two equally probable arrangements of chromosomes at metaphase I

Figure 8.15_s2 Possibility A Possibility B Two equally probable arrangements of chromosomes at metaphase I Metaphase II

Figure 8.15_s3 Possibility A Possibility B Two equally probable arrangements of chromosomes at metaphase I Metaphase II Gametes Combination 1 Combination 2 Combination 3 Combination 4

Figure 8.16Q, 17

Figure 8.17B_1 E C Tetrad (pair of homologous chromosomes in synapsis) c e Breakage of homologous chromatids 1 C E c e Joining of homologous chromatids 2 C E Chiasma c e

Figure 8.17B_2 C E Chiasma c e Separation of homologous chromosomes at anaphase I 3 C E C e E c c e

Figure 8.17B_3 C E C e E c c e Separation of chromatids at anaphase II and completion of meiosis 4 C E Parental type of chromosome C e Recombinant chromosome c E Recombinant chromosome c e Parental type of chromosome Gametes of four genetic types

Hawley, R. S. (2011). "Hitting a Tiny Target in the Dark." Science 331(6019): 870-871.

Figure 8.12A

Figure 8.12A

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