Essential Knowledge: In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis OR

Transcription

1 Essential Knowledge: In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis OR meiosis plus fertilization

2 Objective: You will be able to describe the events that occur in the cell cycle. Do Now: Phase G1 S G2 M

3 The cell cycle is a complex set of stages that is highly regulated with checkpoints, which determine the ultimate fate of the cell. Interphase consists of three phases: G 1 : Growth S: Synthesis of DNA G 2 : Preparation of mitosis Mitosis alternates with interphase in the cell cycle

4 Figure 9.6 G 1 S (DNA synthesis) G Pearson Education, Inc.

5 Cell Specialization When a cell specializes, it often enters into a stage where it no longer divides It can reenter the cell cycle when given appropriate cues Nondividing cells may exit the cell cycle; or hold at a particular stage in the cell cycle

6 The cell cycle is directed by internal controls or checkpoints. Internal and external signals provide stop-and-go signs at the checkpoints. Examples of control include: Mitosis-promoting factor (MPF) Cyclin and cyclin-dependent kinase Action of platelet-derived growth factor (PDGF)

7 Internal Controls or Checkpoints

8 Signaling and the Cell Cycle Internal and external signals provide stop and go signs at checkpoints Example of an internal signal: Mitosis-promoting factor (MPF) Examples of an external signal: Platelet-derived growth factor (PDGF)

9 Internal signal: MPF M G 1 S G 2 M G 1 S G 2 M G 1 MPF activity Cyclin concentration Time (a) Fluctuation of MPF activity and cyclin concentration during the cell cycle Cdk Degraded cyclin Cyclin is degraded G 2 checkpoint Cdk MPF Cyclin (b) Molecular mechanisms that help regulate the cell cycle

10 External signal: PDGF

11 Cancer results from the disruptions in cell cycle control Cancer cells: Do not respond to signals that normally regulate the cell cycle May not need growth factors to grow and divide 2014 Pearson Education, Inc.

12 Objective: You will be able to construct an explanation, using visual representations and narratives, as to how DNA in chromosomes is transmitted to the next generation via mitosis. Do Now:

13 Figure 9.3 Chromosomes because they are condensed Genome 20 m Chromosomes are made of DNA 2014 Pearson Education, Inc.

14 Mitosis passes a complete genome from the parent cell to daughter cells. Mitosis occurs after DNA replication Mitosis followed by cytokinesis produces two genetically identical daughter cells Mitosis plays a role in growth, repair, and asexual reproduction Pearson Education, Inc.

15 Sister chromatids 2014 Pearson Education, Inc.

16 Figure 9.7a 10 m G 2 of Interphase Prophase Prometaphase Centrosomes (with centriole pairs) Chromosomes (duplicated, uncondensed) Early mitotic Centromere spindle Aster Fragments of nuclear envelope Nonkinetochore microtubules Nucleolus Nuclear envelope Plasma membrane Two sister chromatids of one chromosome Kinetochore Kinetochore microtubule

17 Figure 9.7b 10 m Metaphase Anaphase Telophase and Cytokinesis Metaphase plate Cleavage furrow Nucleolus forming Spindle Centrosome at one spindle pole Daughter chromosomes Nuclear envelope forming

18 Mitosis is often followed by cytokinesis

19 Objective: You will be able to construct an explanation, using visual representations and narratives, as to how DNA in chromosomes is transmitted to the next generation via meiosis followed by fertilization. Do Now: 2014 Pearson Education, Inc.

20 Meiosis, a reduction division, followed by fertilization ensures genetic diversity in sexually reproducing organisms Pearson Education, Inc.

21 Figure n 6 Key Maternal set of chromosomes (n 3) Paternal set of chromosomes (n 3) Sister chromatids of one duplicated chromosome Centromere Two nonsister chromatids in a homologous pair Pair of homologous chromosomes (one from each set) 2014 Pearson Education, Inc.

22 Karyotype Homologous Chromosomes Non-homologous 2014 Pearson Education, Inc.

23 Meiosis ensures that each gamete receives one complete haploid (1n) set of chromosomes Pearson Education, Inc.

24 Meiosis divides diploid cells into haploid cells 2014 Pearson Education, Inc.

25 Somatic Cells vs. Gametes Homologous pair 2014 Pearson Education, Inc.

26 Figure 10.7 Interphase Pair of homologous chromosomes in diploid parent cell Duplicated pair of homologous chromosomes Chromosomes duplicate Meiosis I Sister chromatids Diploid cell with duplicated chromosomes Meiosis II Homologous chromosomes separate Haploid cells with duplicated chromosomes 2 1 Sister chromatids separate Haploid cells with unduplicated chromosomes

27 Meiosis During meiosis, homologous chromosomes are paired, with one homologue originating from the maternal and the other from the paternal parent. Orientation of the chromosome pairs is random with respect to the cell poles. Separation of the homologous chromosomes ensures that each gamete receives a haploid (1n) set of chromosomes composed of both maternal and paternal chromosomes. Look at p find where each of the statements above are occurring.

28 Figure 10.5 Key Haploid (n) Diploid (2n) Haploid gametes (n 23) Egg (n) Sperm (n) MEIOSIS FERTILIZATION Ovary Testis Diploid zygote (2n 46) Multicellular diploid adults (2n 46) Mitosis and development

29 Paired Activity Read through the phases of meiosis found on p List what is happening to the DNA at each stage Do NOT include any other material When referring to chromosomes be sure to use either sister chromatids or homologous chromosomes

30 Objective: You will be able to represent the connection between meiosis and increased genetic diversity necessary for evolution. Do Now:

31 Work in pairs Activity One person should have their books open to the mitotic stages One person should have their books open to the meiotic stages For the entire cell cycle, list the similarities between mitosis and meiosis List the differences between mitosis and meiosis

32 Figure 10.9b Property DNA replication Mitosis Occurs during interphase before mitosis begins SUMMARY Meiosis Occurs during interphase before meiosis I begins Number of divisions Synapsis of homologous chromosomes Number of daughter cells and genetic composition Role in the animal body One, including prophase, prometaphase, metaphase, anaphase, and telophase Does not occur Two, each diploid (2n) and genetically identical to the parent cell Enables multicellular adult to arise from zygote; produces cells for growth, repair, and, in some species, asexual reproduction Two, each including prophase, metaphase, anaphase, and telophase Occurs during prophase I along with crossing over between nonsister chromatids; resulting chiasmata hold pairs together due to sister chromatid cohesion Four, each haploid (n), containing half as many chromosomes as the parent cell; genetically different from the parent cell and from each other Produces gametes; reduces number of chromosome sets by half and introduces genetic variability among the gametes

33 Independent Assortment Possibility 1 Possibility 2 Two equally probable arrangements of chromosomes at metaphase I

34 Figure Possibility 1 Possibility 2 Two equally probable arrangements of chromosomes at metaphase I Metaphase II

35 Figure Possibility 1 Possibility 2 Two equally probable arrangements of chromosomes at metaphase I Metaphase II Daughter cells Combination 1 Combination 2 Combination 3 Combination 4

36 During meiosis, homologous chromatids exchange genetic material via a process called crossing over, which increases genetic variation in the resultant gametes

37 Crossing Over Crossing over results form homologous chromosomes exchanging segments of DNA Crossing over begins in prophase I

38 Crossing Over Prophase I of meiosis Pair of homologs Nonsister chromatids held together during synapsis

39 Figure Prophase I of meiosis Pair of homologs Chiasma Nonsister chromatids held together during synapsis Synapsis and crossing over Centromere TEM Anaphase I Breakdown of proteins holding sister chromatid arms together Anaphase II Daughter cells Recombinant chromosomes

40 Fertilization involves the fusion of two gametes It increases genetic variation in populations by providing for new combinations of genetic information in the zygote. It restores the diploid number of chromosomes

41 Random Fertilization Each person can make 8.4 million different sex cells from independent assortment That means parents can produce a zygote with about 70 trillion diploid combinations That s without accounting for crossing over