Chapter 8. Cellular Reproduction: Cells from Cells. Lectures by Edward J. Zalisko

Transcription

1 Chapter 8 Cellular Reproduction: Cells from Cells PowerPoint Lectures for Campbell Essential Biology, Fifth Edition, and Campbell Essential Biology with Physiology, Fourth Edition Eric J. Simon, Jean L. Dickey, and Jane B. Reece Lectures by Edward J. Zalisko 2013 Pearson Education, Inc.

2 WHAT CELL REPRODUCTION ACCOMPLISHES Reproduction may result in the birth of new organisms but more commonly involves the production of new cells. When a cell undergoes reproduction, or cell division, two daughter cells are produced that are genetically identical to each other and to the parent cell Pearson Education, Inc.

3 WHAT CELL REPRODUCTION ACCOMPLISHES Before a parent cell splits into two, it duplicates its chromosomes, the structures that contain most of the cell s DNA. During cell division, each daughter cell receives one identical set of chromosomes from the lone, original parent cell Pearson Education, Inc.

4 WHAT CELL REPRODUCTION ACCOMPLISHES Cell division plays important roles in the lives of organisms. Cell division replaces damaged or lost cells, permits growth, and allows for reproduction. Video: Sea Urchin (time lapse) 2013 Pearson Education, Inc.

5 Figure 8.1a FUNCTIONS OF CELL DIVISION Cell Replacement Growth via Cell Division Human kidney cell LM Early human embryo Colorized SEM

6 WHAT CELL REPRODUCTION ACCOMPLISHES In asexual reproduction, single-celled organisms reproduce by simple cell division and there is no fertilization of an egg by a sperm. Some multicellular organisms, such as sea stars, can grow new individuals from fragmented pieces. Growing a new plant from a clipping is another example of asexual reproduction Pearson Education, Inc.

7 Figure 8.1bb Asexual Reproduction Regeneration of a sea star

8 Figure 8.1bc Asexual Reproduction Reproduction of an African violet from a clipping

9 WHAT CELL REPRODUCTION ACCOMPLISHES In asexual reproduction, the lone parent and its offspring have identical genes. Mitosis is the type of cell division responsible for asexual reproduction and growth and maintenance of multicellular organisms Pearson Education, Inc.

10 WHAT CELL REPRODUCTION ACCOMPLISHES Sexual reproduction requires fertilization of an egg by a sperm using a special type of cell division called meiosis. Thus, sexually reproducing organisms use meiosis for reproduction and mitosis for growth and maintenance Pearson Education, Inc.

11 THE CELL CYCLE AND MITOSIS In a eukaryotic cell, most genes are located on chromosomes in the cell nucleus and a few genes are found in DNA in mitochondria and chloroplasts Pearson Education, Inc.

12 Eukaryotic Chromosomes Each eukaryotic chromosome contains one very long DNA molecule, typically bearing thousands of genes. The number of chromosomes in a eukaryotic cell depends on the species Pearson Education, Inc.

13 Figure 8.2 Species Number of chromosomes in body cells Indian muntjac deer Koala Opossum Giraffe Mouse Human Duck-billed platypus Buffalo Dog Red viscacha rat 102

14 Eukaryotic Chromosomes Chromosomes are made of chromatin, fibers composed of roughly equal amounts of DNA and protein molecules and not visible in a cell until cell division occurs Pearson Education, Inc.

15 Figure 8.3 LM Chromosomes

16 Eukaryotic Chromosomes The DNA in a cell is packed into an elaborate, multilevel system of coiling and folding. Histones are proteins used to package DNA in eukaryotes. Nucleosomes consist of DNA wound around histone molecules. Animation: DNA Packing 2013 Pearson Education, Inc.

17 Figure 8.4 DNA double helix Beads on a string Histones TEM Nucleosome Tight helical fiber Thick supercoil Duplicated chromosomes (sister chromatids) Centromere TEM

18 Figure 8.4a DNA double helix Histones Beads on a string TEM Nucleosome

19 Figure 8.4b Tight helical fiber Thick supercoil Duplicated chromosomes (sister chromatids) Centromere TEM

20 Eukaryotic Chromosomes Before a cell divides, it duplicates all of its chromosomes, resulting in two copies called sister chromatids containing identical genes. Two sister chromatids are joined together tightly at a narrow waist called the centromere Pearson Education, Inc.

21 Eukaryotic Chromosomes When the cell divides, the sister chromatids of a duplicated chromosome separate from each other. Once separated, each chromatid is considered a full-fledged chromosome and identical to the original chromosome Pearson Education, Inc.

22 Figure 8.5 Chromosome duplication Sister chromatids Chromosome distribution to daughter cells

23 The Cell Cycle A cell cycle is the ordered sequence of events that extend from the time a cell is first formed from a dividing parent cell to its own division into two cells. The cell cycle consists of two distinct phases: 1. interphase and 2. the mitotic phase Pearson Education, Inc.

24 Figure 8.6 S phase (DNA synthesis; chromosome duplication) Interphase: metabolism and growth (90% of time) G 1 G 2 Mitotic (M) phase: cell division (10% of time) Cytokinesis (division of cytoplasm) Mitosis (division of nucleus)

25 Figure 8.6a S phase (DNA synthesis; chromosome duplication) Interphase: metabolism and growth (90% of time) G 1 G 2 Mitotic (M) phase: cell division (10% of time)

26 Figure 8.6b Cytokinesis (division of cytoplasm) Mitosis (division of nucleus)

27 The Cell Cycle Most of a cell cycle is spent in interphase. During interphase, a cell performs its normal functions, doubles everything in its cytoplasm, and grows in size Pearson Education, Inc.

28 The Cell Cycle The mitotic (M) phase includes two overlapping processes: 1. mitosis, in which the nucleus and its contents divide evenly into two daughter nuclei and 2. cytokinesis, in which the cytoplasm is divided in two Pearson Education, Inc.

29 Mitosis and Cytokinesis During mitosis the mitotic spindle, a footballshaped structure of microtubules, guides the separation of two sets of daughter chromosomes. Spindle microtubules grow from structures within the cytoplasm called centrosomes Pearson Education, Inc.

30 Mitosis and Cytokinesis Mitosis consists of four distinct phases: 1. Prophase Bioflix Animation: Mitosis Video: Animal Mitosis 2013 Pearson Education, Inc.

31 Figure 8.7a INTERPHASE Centrosomes (with centriole pairs) Chromatin Early mitotic spindle Centrosome PROPHASE Centromere Fragments of nuclear envelope Nuclear envelope Plasma membrane Chromosome (two sister chromatids) Spindle microtubules

32 Figure 8.7aa INTERPHASE Centrosomes (with centriole pairs) Chromatin Early mitotic spindle Centrosome PROPHASE Centromere Fragments of nuclear envelope Nuclear envelope Plasma membrane Chromosome (two sister chromatids) Spindle microtubules

33 Mitosis and Cytokinesis 1. Prophase 2. Metaphase 2013 Pearson Education, Inc.

34 Figure 8.7b METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS Nuclear envelope forming Cleavage furrow Spindle Daughter chromosomes

35 Mitosis and Cytokinesis 1. Prophase 2. Metaphase 3. Anaphase 2013 Pearson Education, Inc.

36 Figure 8.7b METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS Nuclear envelope forming Cleavage furrow Spindle Daughter chromosomes

37 Figure 8.7bc ANAPHASE

38 Mitosis and Cytokinesis 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase 2013 Pearson Education, Inc.

39 Figure 8.7ba METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS Nuclear envelope forming Cleavage furrow Spindle Daughter chromosomes

40 Mitosis and Cytokinesis Cytokinesis usually begins during telophase, divides the cytoplasm, and is different in plant and animal cells Pearson Education, Inc.

41 Mitosis and Cytokinesis In animal cells, cytokinesis is known as cleavage and begins with the appearance of a cleavage furrow, an indentation at the equator of the cell. Animation: Cytokinesis 2013 Pearson Education, Inc.

42 Figure 8.8a SEM Cleavage furrow Cleavage furrow Contracting ring of microfilaments Daughter cells

43 Figure 8.8aa Cleavage furrow Contracting ring of microfilaments Daughter cells

44 Mitosis and Cytokinesis In plant cells, cytokinesis begins when vesicles containing cell wall material collect at the middle of the cell and then fuse, forming a membranous disk called the cell plate. Blast Animation: Cytokinesis in Plant Cells 2013 Pearson Education, Inc.

45 Figure 8.8b Wall of parent cell Cell plate forming Daughter nucleus LM Cell wall Vesicles containing cell wall material Cell plate New cell wall Daughter cells

46 Figure 8.8ba Wall of parent cell Cell plate forming Daughter nucleus LM

47 Figure 8.8bb Cell wall Vesicles containing cell wall material Cell plate New cell wall Daughter cells

48 Cancer Cells: Growing Out of Control Normal plant and animal cells have a cell cycle control system that consists of specialized proteins, which send stop and go-ahead signals at certain key points during the cell cycle Pearson Education, Inc.

49 What Is Cancer? Cancer is a disease of the cell cycle. Cancer cells do not respond normally to the cell cycle control system. Cancer cells can form tumors, abnormally growing masses of body cells. If the abnormal cells remain at the original site, the lump is called a benign tumor Pearson Education, Inc.

50 What Is Cancer? The spread of cancer cells beyond their original site of origin is metastasis. Malignant tumors can spread to other parts of the body and interrupt normal body functions. A person with a malignant tumor is said to have cancer Pearson Education, Inc.

51 Figure 8.9 Lymph vessels Tumor Blood vessel A tumor grows from a single cancer cell. Glandular tissue Cancer cells invade neighboring tissue. Metastasis: Cancer cells spread through lymph and blood vessels to other parts of the body.

52 Cancer Treatment Cancer treatment can involve radiation therapy, which damages DNA and disrupts cell division, and chemotherapy, the use of drugs to disrupt cell division Pearson Education, Inc.

53 Cancer Prevention and Survival Certain behaviors can decrease the risk of cancer: not smoking, exercising adequately, avoiding exposure to the sun, eating a high-fiber, low-fat diet, performing self-exams, and regularly visiting a doctor to identify tumors early Pearson Education, Inc.

54 MEIOSIS, THE BASIS OF SEXUAL REPRODUCTION Sexual reproduction depends on meiosis and fertilization and produces offspring that contain a unique combination of genes from the parents Pearson Education, Inc.

55 Figure 8.10

56 Homologous Chromosomes Different individuals of a single species have the same number and types of chromosomes. A human somatic cell is a typical body cell and has 46 chromosomes Pearson Education, Inc.

57 Homologous Chromosomes A karyotype is an image that reveals an orderly arrangement of chromosomes. Homologous chromosomes are matching pairs of chromosomes that can possess different versions of the same genes Pearson Education, Inc.

58 Figure 8.11 Pair of homologous chromosomes LM Centromere One duplicated chromosome Sister chromatids

59 Homologous Chromosomes Humans have two different sex chromosomes, X and Y, and 22 pairs of matching chromosomes, called autosomes Pearson Education, Inc.

60 Gametes and the Life Cycle of a Sexual Organism The life cycle of a multicellular organism is the sequence of stages leading from the adults of one generation to the adults of the next Pearson Education, Inc.

61 Gametes and the Life Cycle of a Sexual Organism Humans are diploid organisms with body cells containing two sets of chromosomes and haploid gametes that have only one member of each homologous pair of chromosomes. In humans, a haploid sperm fuses with a haploid egg during fertilization to form a diploid zygote Pearson Education, Inc.

62 Figure 8.12 Haploid gametes (n = 23) n Egg cell n Sperm cell MEIOSIS FERTILIZATION Multicellular diploid adults (2n = 46) 2n Diploid zygote (2n = 46) MITOSIS and development Key Haploid (n) Diploid (2n)

63 Gametes and the Life Cycle of a Sexual Organism Sexual life cycles involve an alternation of diploid and haploid stages. Meiosis produces haploid gametes, which keeps the chromosome number from doubling every generation Pearson Education, Inc.

64 Figure Chromosomes duplicate. Pair of homologous chromosomes in diploid parent cell Duplicated pair of homologous chromosomes Sister chromatids INTERPHASE BEFORE MEIOSIS

65 Figure Chromosomes 2 duplicate. Homologous chromosomes separate. Pair of homologous chromosomes in diploid parent cell Duplicated pair of homologous chromosomes Sister chromatids INTERPHASE BEFORE MEIOSIS MEIOSIS I

66 Figure Chromosomes 2 Homologous 3 duplicate. chromosomes separate. Sister chromatids separate. Pair of homologous chromosomes in diploid parent cell Duplicated pair of homologous chromosomes Sister chromatids INTERPHASE BEFORE MEIOSIS MEIOSIS I MEIOSIS II

67 The Process of Meiosis In meiosis, haploid daughter cells are produced in diploid organisms, interphase is followed by two consecutive divisions, meiosis I and meiosis II, and crossing over occurs. Bioflix Animation: Meiosis 2013 Pearson Education, Inc.

68 Figure 8.14a MEIOSIS I: HOMOLOGOUS CHROMOSOMES SEPARATE INTERPHASE PROPHASE I METAPHASE I ANAPHASE I Centrosomes (with centriole pairs) Sites of crossing over Spindle Microtubules attached to chromosome Sister chromatids remain attached Nuclear envelope Chromatin Sister chromatids Pair of homologous chromosomes Centromere Chromosomes duplicate. Homologous chromosomes pair up and exchange segments. Pairs of homologous chromosomes line up. Pairs of homologous chromosomes split up.

69 Figure 8.14aa INTERPHASE Centrosomes (with centriole pairs) Nuclear envelope Chromatin

70 Figure 8.14ab PROPHASE I METAPHASE I ANAPHASE I TELOPHASE I AND CYTOKINESIS Sites of crossing over Spindle Microtubules attached to chromosome Sister chromatids remain attached Cleavage furrow Sister chromatids Pair of homologous chromosomes Centromere

71 Figure 8.14b MEIOSIS II: SISTER CHROMATIDS SEPARATE TELOPHASE I AND CYTOKINESIS PROPHASE II METAPHASE II ANAPHASE II TELOPHASE II AND CYTOKINESIS Cleavage furrow Sister chromatids separate Haploid daughter cells forming Two haploid cells form; chromosomes are still doubled. During another round of cell division, the sister chromatids finally separate; four haploid daughter cells result, containing single chromosomes.

72 Figure 8.14ba PROPHASE II METAPHASE II ANAPHASE II TELOPHASE II AND CYTOKINESIS Sister chromatids separate Haploid daughter cells forming

73 Figure 8.14bb PROPHASE II METAPHASE II

74 Figure 8.14bd ANAPHASE II TELOPHASE II AND CYTOKINESIS Sister chromatids separate Haploid daughter cells forming

75 Review: Comparing Mitosis and Meiosis In mitosis and meiosis, the chromosomes duplicate only once, during the preceding interphase. The number of cell divisions varies: Mitosis uses one division and produces two diploid cells. Meiosis uses two divisions and produces four haploid cells. All the events unique to meiosis occur during meiosis I Pearson Education, Inc.

76 Figure 8.15 MITOSIS MEIOSIS Prophase Duplicated chromosome Metaphase Parent cell Prophase I Metaphase I MEIOSIS I Site of crossing over Chromosomes align. Homologous pairs align. Anaphase Telophase Anaphase I Telophase I MEIOSIS I 2n Sister chromatids separate. 2n Homologous chromosomes separate. Haploid n = 2 MEIOSIS II Sister chromatids separate. n n n n

77 The Origins of Genetic Variation Offspring of sexual reproduction are genetically different from their parents and one another Pearson Education, Inc.

78 Independent Assortment of Chromosomes When aligned during metaphase I of meiosis, the side-by-side orientation of each homologous pair of chromosomes is a matter of chance. Every chromosome pair orients independently of all of the others at metaphase I. For any species, the total number of chromosome combinations that can appear in the gametes due to independent assortment is 2 n, where n is the haploid number Pearson Education, Inc.

79 Independent Assortment of Chromosomes For a human, n = 23. With n = 23, there are 8,388,608 different chromosome combinations possible in a gamete. Animation: Genetic Variation Blast Animation: Genetic Variation: Independent Assortment 2013 Pearson Education, Inc.

80 Figure POSSIBILITY 1 POSSIBILITY 2 Two equally probable arrangements of chromosomes at metaphase of meiosis I

81 Figure POSSIBILITY 1 POSSIBILITY 2 Two equally probable arrangements of chromosomes at metaphase of meiosis I Metaphase of meiosis II

82 Figure POSSIBILITY 1 POSSIBILITY 2 Two equally probable arrangements of chromosomes at metaphase of meiosis I Metaphase of meiosis II Gametes Combination a Combination b Combination c Combination d Because possibilities 1 and 2 are equally likely, the four possible types of gametes will be made in approximately equal numbers.

83 Random Fertilization A human egg cell is fertilized randomly by one sperm, leading to genetic variety in the zygote. If each gamete represents one of 8,388,608 different chromosome combinations, at fertilization, humans would have 8,388,608 8,388,608, or more than 70 trillion different possible chromosome combinations. So we see that the random nature of fertilization adds a huge amount of potential variability to the offspring of sexual reproduction Pearson Education, Inc.

84 Crossing Over In crossing over, nonsister chromatids of homologous chromosomes exchange corresponding segments and genetic recombination, the production of gene combinations different from those carried by parental chromosomes, occurs. Animation: Crossing Over Blast Animation: Genetic Variation: Fusion of Gametes 2013 Pearson Education, Inc.

85 Figure 8.18 Prophase I of meiosis Duplicated pair of homologous chromosomes Homologous chromatids exchange corresponding segments. Chiasma, site of crossing over Metaphase I Sister chromatids remain joined at their centromeres. Metaphase II Spindle microtubule Gametes Recombinant chromosomes combine genetic information from different parents. Recombinant chromosomes

86 Figure 8.18a Prophase I of meiosis Duplicated pair of homologous chromosomes Homologous chromatids exchange corresponding segments. Chiasma, site of crossing over Metaphase I Sister chromatids remain joined at their centromeres. Spindle microtubule

87 Figure 8.18b Metaphase II Gametes Recombinant chromosomes combine genetic information from different parents. Recombinant chromosomes

88 The Process of Science: Do All Animals Have Sex? Observation: No scientists have ever found male bdelloid rotifers, a microscopic freshwater invertebrate. Question: Does this entire class of animals reproduce solely by asexual means? 2013 Pearson Education, Inc.

89 The Process of Science: Do All Animals Have Sex? Hypothesis: Bdelloid rotifers have thrived for millions of years despite a lack of sexual reproduction. Prediction: Bdelloid rotifers would display much more variation in their pairs of homologous genes than most organisms. Experiment: Researchers compared sequences of a particular gene in bdelloid and non-bdelloid rotifers Pearson Education, Inc.

90 The Process of Science: Do All Animals Have Sex? Results: Non-bdelloid sexually reproducing rotifers had a nearly identical homologous gene, differing by only 0.5% on average. The two versions of the same gene in asexually reproducing bdelloid rotifers differed by %. Conclusion: Bdelloid rotifers have evolved for millions of years without any sexual reproduction Pearson Education, Inc.

91 When Meiosis Goes Awry What happens when errors occur in meiosis? Such mistakes can result in genetic abnormalities that range from mild to fatal Pearson Education, Inc.

92 How Accidents during Meiosis Can Alter Chromosome Number In nondisjunction, the members of a chromosome pair fail to separate at anaphase, producing gametes with an incorrect number of chromosomes. Nondisjunction can occur during meiosis I or II Pearson Education, Inc.

93 Figure NONDISJUNCTION IN MEIOSIS I NONDISJUNCTION IN MEIOSIS II Meiosis I Homologous chromosomes fail to separate.

94 Figure NONDISJUNCTION IN MEIOSIS I NONDISJUNCTION IN MEIOSIS II Meiosis I Homologous chromosomes fail to separate. Meiosis II Sister chromatids fail to separate.

95 Figure NONDISJUNCTION IN MEIOSIS I NONDISJUNCTION IN MEIOSIS II Meiosis I Homologous chromosomes fail to separate. Meiosis II Sister chromatids fail to separate. Gametes n + 1 n + 1 n 1 n 1 n + 1 n 1 Abnormal Abnormal n n Normal

96 How Accidents during Meiosis Can Alter Chromosome Number If nondisjunction occurs, and a normal sperm fertilizes an egg with an extra chromosome, the result is a zygote with a total of 2n + 1 chromosomes. If the organism survives, it will have an abnormal karyotype and probably a syndrome of disorders caused by the abnormal number of genes Pearson Education, Inc.

97 Figure 8.21 Abnormal egg cell with extra chromosome n + 1 Normal sperm cell n (normal) Abnormal zygote with extra chromosome 2n + 1

98 Down Syndrome: An Extra Chromosome 21 Down syndrome is also called trisomy 21, is a condition in which an individual has an extra chromosome 21, and affects about one out of every 700 children Pearson Education, Inc.

99 Figure 8.22 LM Trisomy 21

100 Figure 8.22a LM Trisomy 21

101 Figure 8.22b

102 Down Syndrome: An Extra Chromosome 21 The incidence of Down syndrome in the offspring of normal parents increases markedly with the age of the mother Pearson Education, Inc.

103 Figure 8.23 Infants with Down syndrome (per 1,000 births) Age of mother

104 Abnormal Numbers of Sex Chromosomes Nondisjunction in meiosis can lead to abnormal numbers of sex chromosomes but seems to upset the genetic balance less than unusual numbers of autosomes, perhaps because the Y chromosome is very small and carries relatively few genes Pearson Education, Inc.

105 Table 8.1

106 Evolution Connection: The Advantages of Sex Asexual reproduction conveys an evolutionary advantage when plants are sparsely distributed and unlikely to be able to exchange pollen or superbly suited to a stable environment. Asexual reproduction also eliminates the need to expend energy forming gametes and copulating with a partner Pearson Education, Inc.

107 Figure 8.24 Runner

108 Evolution Connection: The Advantages of Sex Sexual reproduction may convey an evolutionary advantage by speeding adaptation to a changing environment or allowing a population to more easily rid itself of harmful genes Pearson Education, Inc.

109 Figure 8.UN01 Duplication of all chromosomes Distribution via mitosis Genetically identical daughter cells

110 Figure 8.UN02 Chromosome (one long piece of DNA) Centromere Sister chromatids Duplicated chromosome

111 Figure 8.UN03 S phase DNA synthesis; chromosome duplication Interphase Cell growth and chromosome duplication G 1 G 2 Mitotic (M) phase Genetically identical daughter cells Cytokinesis (division of cytoplasm) Mitosis (division of nucleus)

112 Figure 8.UN04 Human Life Cycle Haploid gametes (n = 23) Key Haploid (n) Diploid (2n) n Egg cell n Sperm cell MEIOSIS FERTILIZATION Male and female diploid adults (2n = 46) MITOSIS and development 2n Diploid zygote (2n = 46)

113 Figure 8.UN05 MITOSIS Parent cell (2n) Chromosome duplication Parent cell (2n) Chromosome duplication MEIOSIS MEIOSIS I Pairing of homologous chromosome Crossing over Daughter cells 2n 2n MEIOSIS II n n n Daughter cells n

114 Figure 8.UN06 LM (a) (b) (c) (d)