Chapter 9 Sexual Reproduction and Meiosis

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2 Chapter 9 Sexual Reproduction and Meiosis Ultrasound: Chad Ehlers/Glow Images Copyright McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

by binary fission: Carolina Biological Supply Section 9.

3 What are the 2 forms of reproduction? 1) Asexual 2) Sexual Human family: Corbis RF; Amoeba reproducing by binary fission: Carolina Biological Supply Section 9.1 Company/Phototake; Mother cat and kittens: Jane Burton/Dorling Kindersley/Getty Images Figure 9.1

4 Why Sex? Genetic diversity Increases chance to survive Section 9.1 Figure 9.2

5 Semen attack unsuspecting ovum

6 Figure 8.11 Homologous chromosomes Pair of homologous chromosomes Locus Centromere Sister chromatids One duplicated chromosome

7 Diploid Cells Contain Two Homologous Sets of Chromosomes Most cells in a sexually reproducing organism have two sets of chromosomes: one from the father and one from the mother. Section 9.2 All karyotype photos: CNRI/Science Source Figure 9.3

8 Diploid Cells Contain Two Homologous Sets of Chromosomes Homologous pair: look alike chromosomes carry the same sequence of genes for the same traits ALLELES different versions Section 9.2 Figure 9.4

The photo below shows two chromosomes from one cell. Which statement is true? A. Both came from the person s mother. B. The 1-2 pair is identical to the 3-4 pair.

9 The photo below shows two chromosomes from one cell. Which statement is true? A. Both came from the person s mother. B. The 1-2 pair is identical to the 3-4 pair. C. 1 is identical to 2. D. The chromosomes have not been replicated yet Flower: Doug Sherman/Geofile/RF

10 Figure 8.12A Haploid gametes (n 23) n Egg cell n Sperm cell Meiosis Fertilization Ovary Testis Diploid zygote (2n 46) 2n Multicellular diploid adults (2n 46) Mitosis Key Haploid stage (n) Diploid stage (2n)

11 Meiosis Overview

12 Meiosis Overview Meiosis scrambles alleles halves the chromosome number 2n=4 MEIOSIS I n=2 MEIOSIS II n=2 Section 9.3 Human female karyotype: James Cavallini/Science Source Figure 9.6

13 Figure 8.12B INTERPHASE MEIOSIS I MEIOSIS II Sister chromatids A pair of homologous chromosomes in a diploid parent cell A pair of duplicated homologous chromosomes

14 In Meiosis, DNA Replicates Once, but the Nucleus Divides Twice 2n=4 Section 9.4 All photos Ed Reschke Figure 9.7

15 In Meiosis, DNA Replicates Once, but the Nucleus Divides Twice n=2 Section 9.4 All photos Ed Reschke Figure 9.7

16 Figure 8.13_3 Telophase I and Cytokinesis Cleavage furrow

17 Figure 8.13_4 MEIOSIS II: Sister chromatids separate Prophase II Metaphase II Anaphase II Telophase II and Cytokinesis Sister chromatids separate Haploid daughter cells forming

18 Interphase

19 Meiosis I Prophase I Synapsis Tetrad formation Crossing over

20 Meiosis I Meiosis Generates Variability During crossing over, two homologous chromosomes exchange genetic material during prophase I. Section 9.5 Figure 9.8

21 Figure 8.16 Meiosis I Crossing Over What are the results for the chromosomes after crossing over? Coat-color genes Eye-color genes Brown C Black E Meiosis C C E E Brown coat (C); black eyes (E) c e c White e Pink c e Tetrad in parent cell (homologous pair of duplicated chromosomes) Chromosomes of the four gametes White coat (c); pink eyes (e)

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

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

24 Meiosis I Metaphase I Metaphase plate Independent assortment 2 n 2 23 => 8 million

25 Meiosis I Meiosis Generates Variability In independent assortment, chromosome pairs align randomly during metaphase I. Section 9.5 Figure 9.9

26 Figure 8.15_s1 Meiosis I Independent Assortment Possibility A Possibility B Two equally probable arrangements of chromosomes at metaphase I

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

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

29 Meiosis I Anaphase I Homologous chromosomes separate Sister chromatids attached

30 Meiosis I Telophase I & Cytokinesis Cleavage furrow Cell Plate 2 cells Haploid Sister chromatids attached

31 Half Time! Rest break Reformation of nucleus, nucleolus, etc. NO MORE DNA Replication!!! Temporary, if it occurs at all

32 Meiosis II Prophase II Same as prophase of mitosis

33 Meiosis II Metaphase II Metaphase plate Line up single file

34 Meiosis II Anaphase II Sister chromatids separate

35 Meiosis II Telophase II & Cytokinesis 4 cells haploid variation

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

37 Meiosis Produces Human Gametes Sperm cells form in the testes. Egg cells form in the ovaries. Section 9.8 Sperm contacting egg: Francis Leroy, Biocosmos/Science Source Figure 9.15

38 Meiosis Produces Human Gametes Section 9.8 Figure 9.16

39 Meiosis Produces Human Gametes Section 9.8 Figure 9.17

40 Spermatogenesis Spermatogenesis Puberty 4 potential sperm Acrosome cap

41 Mature Sperm

42 Oogenesis Oogenesis Prior to birth (7 month) Arrested: Prophase I Puberty Arrested: Metaphase II Fertilization Completion of meiosis Polar bodies

43 Ovum development

44 Meiosis Generates Variability Identical twins: embryo splits in two Each embryo then develops independently Section 9.5 Identical twins: Barbara Penoyar/Getty Images RF Figure 9.10

45 Meiosis Generates Variability Fraternal twins: two sperm cells fertilize two separate egg cells Section 9.5 Fraternal twins: Image Source Black/ Getty Images RF Figure 9.10

46 Many sets of triplets consist of a pair and a spare; that is, two identical babies and one non-identical baby. Producing this arrangement requires sperm and eggs. A. 2 2 B. 1 3 C. 3 1 D. 2 3 Flower: Doug Sherman/Geofile/RF

47 Karyotyping

48 Human Karyotypes

49 Figure 8.20A_s3 MEIOSIS I Nondisjunction Nondisjunction MEIOSIS II Normal meiosis II Gametes Number of chromosomes n 1 n 1 n 1 n 1 Abnormal gametes

50 Figure 8.20B_s3 MEIOSIS I Nondisjunction Normal meiosis I MEIOSIS II Nondisjunction n 1 n 1 n n Abnormal gametes Normal gametes

51 Nondisjunction

52 Nondisjuction & Fertilization

53 Figure 8.19A Trisomy 21

54 Downs Syndrome & Maternal Age

55 Figure 8.23A Chromosomal Alterations Deletion Inversion Duplication Reciprocal translocation Homologous chromosomes Nonhomologous chromosomes

56 Figure 8.23B Chromosomal Alterations Reciprocal translocation Chromosome 9 Chromosome 22 Reciprocal translocation Activated cancer-causing gene Philadelphia chromosome

57 Errors Also Occur Within Chromosomes Mutations in chromosome structure can have major effects on an organism. Section 9.7 Chromosomes: Addenbrookes Hospital/Science Source Figure 9.14

58 Klinefelter s Syndrome

59 Klinefelter s Syndrome

60 Turner s Syndrome

61 XYY Super Male

62 Mitosis Meiosis Number of chromosomal duplications Number of cell divisions Number of daughter cells produced Number of chromosomes in the daughter cells How the chromosomes line up during metaphase Genetic relationship of the daughter cells to the parent cell Functions performed in the human body

Sexual Reproduction and Meiosis

Sexual Reproduction and Meiosis Ultrasound: Chad Ehlers/Glow Images Copyright McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill