BIOL 2296 Chapter Notes - Chapter 12.5, 12.6: Chromosome Segregation, Sister Chromatids, Cenpa

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13 Apr 2019

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Learning objectives: contrast the dna sequences dictating centromere formation in yeast and in higher. 12. 5 chromosome segregation eukaryotes: describe spindle attachment during metaphase and the role tension on kinetochores plays in ensuring proper chromosome segregation, compare the behavior of cohesin complexes during mitosis, meiosis i, and meiosis ii. Kitentochore attachment: kinetochores assemble at centromeres, chromosomes attach to microtubules of mitotic spindle at the kinetochore. H3 / cenp-a: chromatin is packaged differently at the centromere, h3 is replaced by histone variant cenp-a, cenp-a nucleosomes act as scaffolds for many kinetochore proteins. Action of cohesin during mitosis: cohesin is a protein complex that holds sister chromatids together during metaphase, at anaphase, cohesin is enzymatically cleaved and sister chromatids are released from each other. Action of cohesin during meiosis i: at anaphase i, cohesin along chromosome arms is enzymatically cleaved but cohesin at centromeres is not cleaved.

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Part A- Microtubules. Select all that apply.

1) They are filaments in mitotic and meiotic spindles

2) They are required for moving sister chromatids to opposite sides of the poles during anaphase II of meiosis and anaphase of mitosis.

3) They are required for moving homologs to opposite sides of the poles during anaphase I of meiosis.

4) They are important for maintaining homologous chromosome pairing and plays a role in recombination.

5) They catalyze the phosphorylation of specific proteins.

6) They are a layered structue located between paired homologs in prophase I of meiosis in many organisms.

Part B- Cyclin-dependent kinases. Select all that apply.

1) They are filaments in mitotic and meiotic spindles.

2) They are enzymes that control progression through cell cycle.

3) They are required for the segregation of chromosomes during anaphase of mitosis or meiosis.

4) They are important for homologous chromosome pairing and plays a role in recombination.

5) They catalyze the phosphorylation of specific proteins.

Part C- Kinetochores. Select all that apply.

1) They are enzymes that control progression through cell cycle.

2) They are important for maintaining homologous chromosome pairing and plays a role in recombination.

3) They are required for the segregation of chromosomes during anaphase of mitosis or meiosis.

4) They are complx structures attached to the centromeres of chromosomes that bind to spindle microtubules.

5) They catalyze the phosphorylation of specific proteins.

Part D- Synaptonemal complex. Select all that apply.

1) It is required for moving sister chromatids to opposite sides of the poles during anaphase II of meiosis and anaphase of mitosis.

2) It is a layered structure located between paired homologs in prophase I of meiosis in many organisms.

3) It is complex structures attached to the centromeres of chromosomes that bind to spindle microtubules.

4) It catalyzes the phospohorylation of specific proteins.

5) It is important for maintaining homologous chromosome pairing and plays a role in recombination.

31.????? interphase A. cytoplasm divided between the two daughter cells

32.????? chromosomenumber B. final phase of mitosis; daughter nuclei form

33.????? chromatid C. sum total of chromosomes in all cells of a given

type

34.????? cytokinesis D. chromosomes condense and mitotic spindle

begins to form

35.????? metaphase E. chromosomes line up at spindle equator

36.????? alleles F. sister chromatids separate, move to opposite

spindle poles now

37.????? prophase G. none between meiosis I and II

38.????? telophase H. half of a chromosome in prophase

39. ????? anaphase I. different molecular forms of the same gene

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Carefully read the following statements about cell division (1) After meiosis, the number of chromosomes in the newly formed cell is the same as that in the parent cell. Whereas, in mitosis, the chromosome number in daughter cell is reduced to half. (2) Cytokinesis is a highly regulated event in which cellular organelles are evenly distributed forming two daughter cells. (3) In Meiosis, DNA replication occurs only once whereas the cells divide twice and it is the mechanism that produces genetic variation in daughter cells. (4) In diplotene, chiasmata are formed between homologous chromosomes followed by crossing over and segregation of sister chromatids. (5)The kinetochore is a DNA protein complex which serves as the attachment point for spindle fibers. Which of the above statement or combination of statements is correct?

BIOL 2296 Chapter Notes - Chapter 12.5, 12.6: Chromosome Segregation, Sister Chromatids, Cenpa

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