Chapter 2 Lecture. Copyright 2009 Pearson Education, Inc.

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1 Chapter 2 Lecture Mitosis Click to and edit Meiosis Master tit Copyright 2009 Pearson Education, Inc.

2 2.1 Cell Structure Is Closely Tied to Genetic Function Copyright 2009 Pearson Education, Inc.

3 Copyright 2009 Pearson Education, Inc. Figure 2.1

4 Copyright 2009 Pearson Education, Inc. Figure 2.2

5 2.2 Chromosomes Exist in Homologous Pairs in Diploid Organisms Copyright 2009 Pearson Education, Inc.

6 DNA is the hereditary material Ordered into chromosomes 1. eukaryotes, many chromosomes 2. prokaryotes, single chromosome

7 Different species often have different numbers of chromosomes Haploid number (n): Human: 23 Chimpanzee: 24 Mouse: 20 Cattle: 30 Chicken: 39 Frog: 13 House fly: 6 Fruit fly: 4 Jack jumper ant: 1 Corn: 10 Cotton: 26 Garden pea: 7 Mustard plant: 5 Tobacco: 24 Green alga: 18 Pink bread mold: 7 Yeast: 16 horsetail plant: 108

8 All somatic cells derived from members of the same species contain an identical number of chromosomes (rare exceptions). In diploid organisms, nearly all chromosomes exist in pairs with regard to chromosome lengths and centromere placements. The members of each pair are called homologous chromosomes. Homologous chromosomes usually contain nearly identical genetic information.

9 An organism (cell) is defined as a diploid if each member of the chromosomes has just two (a pair) homologous chromosomes: Human body (diploid) 2n = 46, two sets Egg or sperm (haploid) n = 23, one set Polyploids: Cells or organisms having more than two sets of chromosomes: triploid (3n), tetraploid (4n), pentaploid (5n), hexaploid (6n), etc.

10 Copyright 2009 Pearson Education, Inc. Figure 2.3

11 Copyright 2009 Pearson Education, Inc. Figure 2.4

12 Human male karyotype Copyright 2009 Pearson Education, Inc. Figure 2-4b Copyright 2006 Pearson Prentice Hall, Inc.

13 Copyright 2009 Pearson Education, Inc. Human female karyotype

14 Copyright 2009 Pearson Education, Inc. Table 2.1

15 2.3 Mitosis Partitions Chromosomes into Dividing Cells - Mitosis leads to the production of two cells, each with the same number of chromosomes as the parental cell and the identical genetic content. - Meiosis reduces the genetic content and the number of chromosomes by precisely half. Copyright 2009 Pearson Education, Inc.

16 Mitosis faithful copying of DNA from one cell to next. cell division without ploidy reduction development of multicellular organisms asexual reproduction of unicellular organisms Copyright 2009 Pearson Education, Inc.

17 Copyright 2009 Pearson Education, Inc. Figure 2.5

18 Copyright 2009 Pearson Education, Inc.

19 What Is the Universe Made Of? What is the Biological Basis of Consciousness? Why Do Humans Have So Few Genes? To What Extent Are Genetic Variation and Personal Health Linked? Can the Laws of Physics Be Unified? How Much Can Human Life Span Be Extended? What Controls Organ Regeneration? How Can a Skin Cell Become a Nerve Cell? How Does a Single Somatic Cell Become a Whole Plant? Copyright 2009 Pearson Education, Inc.

20 Copyright 2009 Pearson Education, Inc. Figure 2.6

21 Copyright 2009 Pearson Education, Inc. Figure 2.7a

22 Copyright 2009 Pearson Education, Inc.

23 !!!!!

24 Copyright 2009 Pearson Education, Inc.

25 2.4 Meiosis Reduces the Chromosome Number from Diploid to Haploid in Germ Cells and Spores Copyright 2009 Pearson Education, Inc.

26 Meiosis Reduces the chromosome number from diploid to haploid in germ cells and spores. During sexual reproduction, gametes then combine in fertilization to reconstitute the diploid complement found in parental cells. Reshuffles the genetic material. It generates gametes with many combinations of maternally and paternally derived chromosomes among the haploid complement (independent assortment). Crossing over results in genetic exchange between members of each homologous pair of chromosomes. Copyright 2009 Pearson Education, Inc.

27 Copyright 2009 Pearson Education, Inc.

28 Chromatin begins to condense and chromosomes become visible. Initial pairing of homologous chromosomes (300 nm apart). Bivalent More intimate pairing: synapsis (100 nm apart). Sister chromatids are visible: tetrad Homologous chromosomes begin to separate except at Chiasma Copyright 2009 Pearson Education, Inc. Chromosomes further pull apart. Chiasmata move to ends of tetrads. Nuclear envelope breaks down, centromeres present on equatorial plate

29 Reductional division Copyright 2009 Pearson Education, Inc.

30 The Second Meiotic Division Equational division Copyright 2009 Pearson Education, Inc.

31 Copyright 2009 Pearson Education, Inc.

32 2.5 The Development of Gametes Varies in Spermatogenesis Compared to Oogenesis Copyright 2009 Pearson Education, Inc.

33 Undifferentiated diploid germ cell In humans, oogenesis begins in embryonic ovary, but arrests at prophase I. Meiosis resumes just before ovulation and completes after fertilization Copyright 2009 Pearson Education, Inc.

34 Twins provide an excellent means of studying genetics of traits monozygotic (identical) twins have the exact same genome separated only by mitosis fraternal twins are no more related than other siblings separated by two meioses

35 2.6 Meiosis Is Critical to the Successful Sexual Reproduction of All Diploid Organisms Copyright 2009 Pearson Education, Inc.

36 Animals have evolved a separate germline that is distinct from the soma or somatic tissue. Plants, fungi, and unicellular eukaryotes (obviously) lack a germline. Copyright 2009 Pearson Education, Inc.

37 Copyright 2009 Pearson Education, Inc.

38 2.7 Electron Microscopy Has Revealed the Physical Structure of Mitotic and Meiotic Chromosomes Copyright 2009 Pearson Education, Inc.

39 Copyright 2009 Pearson Education, Inc. Figure 2.14