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Inquiry into Life Twelfth Edition Chapter 5 Lecture PowerPoint to accompany Sylvia S. Mader Copyright © The McGraw-Hill Companies, Inc. Permission required.

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Presentation on theme: "Inquiry into Life Twelfth Edition Chapter 5 Lecture PowerPoint to accompany Sylvia S. Mader Copyright © The McGraw-Hill Companies, Inc. Permission required."— Presentation transcript:

1 Inquiry into Life Twelfth Edition Chapter 5 Lecture PowerPoint to accompany Sylvia S. Mader Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 5.1 Cell Increase and Decrease Cell division increase the number of somatic cells (body cells)

3 5.1 Cell Increase and Decrease Cell division increase the number of somatic cells (body cells) ZygoteTrillions of cells

4 5.1 Cell Increase and Decrease Cell division increase the number of somatic cells (body cells) –Mitosis: Division of the nucleus

5 5.1 Cell Increase and Decrease Cell division increase the number of somatic cells (body cells) –Mitosis: Division of the nucleus –Cytokinesis:Division of the cytoplasm

6 5.1 Cell Increase and Decrease Cell division increase the number of somatic cells (body cells) –Mitosis: Division of the nucleus –Cytokinesis:Division of the cytoplasm –Apoptosis:Programmed cell death

7 5.1 Cell Increase and Decrease The Cell Cycle –Orderly set of stages that occur between the time a cell divides and the time the resulting daughter cells divide

8 5.1 Cell Increase and Decrease The Cell Cycle –Interphase G 1 S G 2 –Mitotic Stage Mitosis and Cytokinesis

9 5.1 Cell Increase and Decrease The Cell Cycle –Interphase G 1 S G 2 –Mitotic Stage Mitosis and Cytokinesis

10 The Cell Cycle

11 5.1 Cell Increase and Decrease Control of the Cell Cycle –Internal and External Signals Signaling proteins called cyclins increase and decrease as the cell cycle continues –Three Checkpoints G 1 G 2 M

12 The Cell Cycle

13 5.1 Cell Increase and Decrease Apoptosis – Cells undergo programmed cell death when they cannot complete mitosis or in response to external signals.

14 Apoptosis

15 5.2 Maintaining the Chromosome Number

16 Terms: –Chromatin: tangled mass of threadlike DNA in a non-dividing cell

17 5.2 Maintaining the Chromosome Number Terms: –Chromatin: tangled mass of threadlike DNA in a non-dividing cell –Chromosomes: condensed DNA molecules observed in dividing cells

18 5.2 Maintaining the Chromosome Number Terms: –Chromatin: tangled mass of threadlike DNA in a non-dividing cell –Chromosomes: condensed DNA molecules observed in dividing cells –Diploid (2n): Cells have two (a pair) of each type of chromosome

19 5.2 Maintaining the Chromosome Number Terms: –Chromatin: tangled mass of threadlike DNA in a non-dividing cell –Chromosomes: condensed DNA molecules observed in dividing cells –Diploid (2n): Cells have two (a pair) of each type of chromosome –Haploid (1n): Cells have half the diploid number of chromosomes

20 5.2 Maintaining the Chromosome Number Overview of Mitosis –Nuclear division in which chromosome number stays constant –DNA replication produces duplicated chromosomes –Each duplicated chromosome is composed of 2 sister chromatids held together by a centromere –Sister chromatids are genetically identical –During mitosis, the centromere divides and each chromatid becomes a daughter chromosome

21 Chromosomes and Chromatids

22 Mitosis Overview

23 5.2 Maintaining the Chromosome Number Mitosis in Detail - Animal Cells –Prophase-nuclear membrane disappears, centrosomes migrate, spindle fibers appear –Metaphase-chromosomes line up at metaphase plate, associated with spindle fibers –Anaphase-centromeres divide, sister chromatids migrate to opposite poles, cytokinesis begins –Telophase-nuclear membranes form, spindle disappears, cytokinesis occurs

24 Mitosis in Detail - Animal Cells

25 5.2 Maintaining the Chromosome Number How Plant Cells Divide –Occurs in meristematic tissues –Same phases as animal cells –Plant cells do not have centrioles or asters

26 Mitosis in Detail - Plant Cells

27 5.2 Maintaining the Chromosome Number Cytokinesis in Plant Cells –Flattened, small disk appears between daughter cells –Golgi apparatus produces vesicles which move to disk –Release molecules which build new cell walls –Vesicle membranes complete plasma membranes

28 Cytokinesis in Plant Cells

29 5.2 Maintaining the Chromosome Number Cytokinesis in Animal Cells Cleavage furrow forms between daughter nuclei Contractile ring contracts deepening the furrow Continues until separation is complete

30 Cytokinesis in Animal Cells

31 5.2 Maintaining the Chromosome Number Cell Division in Prokaryotes: Binary Fission –Prokaryotes have a single chromosome –Chromosomal replication occurs before division –Cell begins to elongate to twice its length –Cell membrane grows inward until division is complete

32 Binary Fission

33 5.3 Reducing the Chromosome Number

34 Meiosis –Occurs in the life cycle of sexually reproducing organisms –Reduces the chromosome number –Provides offspring with a different combination of traits from that of either parent

35 5.3 Reducing the Chromosome Number Overview of Meiosis –2 divisions, 4 daughter cells –Cells are diploid at beginning of meiosis –Pairs of chromosomes are called homologues

36 5.3 Reducing the Chromosome Number Overview of Meiosis –Meiosis I Homologues line up side by side at equator- synapsis When pairs separate, each daughter cell receives one member of the pair Cells are now haploid

37 Meiosis

38 5.3 Reducing the Chromosome Number Overview of Meiosis –Meiosis II No replication of DNA occurs in this division Centromeres divide and sister chromatids migrate to opposite poles to become individual chromosomes Each of the four daughter cells produced has the haploid chromosome number and each chromosome is composed of one chromatid

39 Meiosis

40 5.3 Reducing the Chromosome Number Overview of Meiosis –Fertilization Fertilization restores the diploid number of chromosomes in a cell that will develop into a new individual.

41 5.3 Reducing the Chromosome Number Meiosis in Detail –Genetic Recombination Occurs in Two Ways Crossing Over Independent Assortment

42 Crossing Over

43 Independent Assortment

44 5.3 Reducing the Chromosome Number Phases of Meiosis I –Prophase I Synapsis occurs, nuclear membrane breaks down Homologues line up side by side and crossing over occurs –Metaphase I Homologous pairs line up at metaphase plate such that maternal or paternal member may be oriented toward either pole

45 5.3 Reducing the Chromosome Number Phases of Meiosis I Anaphase I Homologous chromosomes (each still consisting of 2 chromatids) undergo independent assortment into daughter cells –Telophase I Cytokinesis produces 2 daughter cells which are haploid

46 Phases of Meiosis I Fig 5.12

47 5.3 Reducing the Chromosome Number Interkinesis - period of time between Meiosis I and Meiosis II Phases of Meiosis II –Prophase II- Cells have one member of each homologous pair –Metaphase II Chromosomes line up at the metaphase plate

48 5.3 Reducing the Chromosome Number Phases of Meiosis II –Anaphase II Centromeres divide and daughter chromosomes migrate –Telophase II Nuclei form, cytokinesis

49 Phases of Meiosis II Fig 5.13

50 5.3 Reducing the Chromosome Number Nondisjunction –The failure of paired chromosomes or chromatids to separate during cell division –Results in cells with an abnormal number of chromosomes –Trisomy 21 (Down syndrome) is an example

51 5.3 Reducing the Chromosome Number Genetic Recombination –Promotes genetic variability –Independent assortment of paired chromosomes during metaphase I –Crossing over in prophase I –Both assure that gametes will contain different combinations of chromosomes –When fertilization occurs, the resulting offspring will be genetically unique

52 Comparison of Meiosis to Mitosis DNA replication occurs only once prior to either meiosis and mitosis Meiosis requires two divisions, mitosis only one Meiosis produces four daughter cells, mitosis produces two Daughter cells from meiosis are haploid, those from mitosis are diploid Daughter cells from meiosis are genetically variable, while those from mitosis are genetically identical

53 Comparison of Meiosis to Mitosis

54 5.5 The Human Life Cycle Requires both mitosis and meiosis Meiosis in the female is called oogenesis Meiosis in the male is called spermatogenesis At fertilization, the resulting zygote divides by mitosis for the processes of growth and development Mitosis is used for repair throughout life

55 Life Cycle of Humans

56 5.5 The Human Life Cycle Spermatogenesis –Begins at puberty and continues throughout life –Primary spermatocytes (2n) divide in meiosis I to form two secondary spermatocytes (1n) –Secondary spermatocytes divide in meiosis II to produce four sperm

57 5.5 The Human Life Cycle Oogenesis –Begins in the fetus Primary oocytes are arrested in prophase I –At puberty, one primary oocyte continues the process of meiosis during each menstrual cycle –Primary oocyte (2n) divides in meiosis I to produce one secondary oocyte (1n) and one polar body Division is unequal as secondary oocyte receives most of the cell contents and half the chromosomes

58 5.5 The Human Life Cycle Oogenesis –If the secondary oocyte is fertilized, meiosis II will proceed. Another unequal division will occur, the egg receiving most of the cytosplasm. A second polar body is also formed. –The unequal divisions allows the egg to have all the cellular “machinery” it needs for embryonic development

59 Spermatogenesis and Oogenesis in Mammals

60 5.5 The Human Life Cycle Summary –Spermatogenesis and oogenesis both utilize meiosis –Spermatogenesis begins at puberty and continues throughout life –Spermatogenesis produces one sperm per primary spermatocyte Results in production of many sperm –Oogenesis results in one oocyte and up to three polar bodies per primary oocyte Divisions are unequal, ovum receives most cell contents –Oogenesis begins prior to birth, stops until puberty, then resumes in a cyclic pattern –Cyclic release of oocytes continues until menopause when the process stops


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