8.3.4 Disjunction and Meiosis II

Question 1

note

Answer 1

• Two general adaptations of meiosis are to form haploid cells from diploid cells and to segregate homologous chromosomes into separate cells.
  • The process of meiosis involves two divisions with phases in each division similar to the phases in mitosis. The first division (meiosis I), involves splitting the homologous chromosomes from each other into two different cells. The second division (meiosis II), involves separating sister chromatids of a replicated chromosome into two different cells.

Question 2

meiosis I & II

Answer 2

• Prophase I: After homologous chromosomes synapse,
  chiasmata form between regions of the synapsed
  chromosomes.
• Metaphase I: Homologous pairs line up at the equator of the cell. This alignment organizes the homologues so that they will be divided evenly.
• Anaphase I: Homologues separate and migrate to opposite ends of the cell.
• Telophase I: The cell divides to form two cells, each with one chromosome from a homologous pair. The chromosomes will decondense.
• Prophase II: The chromosomes recondense and the spindle fibers re-form.
• Metaphase II: As the spindle fibers attach to the
  centromeres, the chromosomes align at the equator of the cell.
• Anaphase II: Chromatids of each chromosome break apart and migrate to opposite ends of the cell.
• Telophase II: The cells eventually divide and the nuclei
  reform.
• The cells resulting from meiosis have half the number of chromosomes of the parent cell (they are haploid). Haploid cells that are able to take part in sexual reproduction are called gametes.

Question 3

Which statement regarding meiosis is true?

Answer 3

• Homologous chromosomes separate during anaphase I

Question 4

If we count copies (c) of DNA, what do we start and end with in the process of meiosis?

Answer 4

• 4c to 1c

Question 5

Homologous chromosomes separate and migrate to opposite poles during

Answer 5

• anaphase I

Question 6

Which statement regarding disjunction is false?

Answer 6

• Disjunction occurs only during anaphase II of meiosis

Question 7

Sister chromatids of each chromosome separate and move to opposite poles during

Answer 7

• anaphase II.