Biology 203 Unit 3: Study Guide

Question

Define meiosis. Describe what takes place during each of the phases of meiosis.

a.      Interphase

b.      Prophase I

c.      Metaphase I

d.      Anaphase I

e.      Telophase I

f.       Cytokinesis

g.     Prophase II

h.      Metaphase II

i.        Anaphase II

j.       Telophase II

k.      Cytokinesis

Answer 1

1. Interphase- all of the cell cycle expect mitosis, Surface Area to Volume ratio decreases
2. G1 phase- Increase in size, organelles needed by the cell are formed
3. S phase- DNA replication
4. G2 phase- All proteins needed for mitosis are formed
5. Prophase I:
6. Supercoiling of chromatin into chromosomes
7. Homologous chromosomes (4 sister chromatids) align forming a "bivalent"
8. Chiasma (synapsis)- location for crossing over or exchange of genetic material (cause of variation)
9. Recombinants (homologous chromosomes after genetic material has been exchanged) are formed
10. Metaphase I:
11. Nuclear membrane disappears
12. Chromosomes line up at the equator of the cell in double rows
13. Microtubules (spindle fibers) extend to each chromosome forming the meiotic spindle
14. Random orientation of homologous (parental/ maternal) chromosomes= source of variation
15. Anaphase I:
16. Complete chromosomes (sister chromatids still attached) are pulled to opposite poles
17. Random assortment- cause of variation because some parental and some maternal go to one cell or the other
18. Telophase I: 2 cells, each chromosome is made of sister chromatids
19. Female ovaries develop over long periods
20. Nuclear envelope reforms
21. Uncoiling of chromosomes
22. Male gametes go from 1st meiotic division to 2nd meiotic division right away
23. Cytokinesesis: cleavage furrow of cytoplasm and cell membrane
24. Diploid cell splits into 2 haploid cells
25. Prophase II: supercoiling of chromosomes (females)
26. Metaphase II
27. Nuclear membrane disappears
28. Chromosomes line up at center of the cell
29. Sister chromatids are pulled apart
30. Nondisjunction- failure of sister chromatids to separate (source of mutation)
31. Anaphase II: sister chromatids pulled to opposite poles (source of variation)
32. Telophase II:
33. Nuclear envelope reforms
34. Uncoiling of chromosomes
35. Cytokinesesis: cleavage furrow of cytoplasm and cell membrane
36. 2 haploid cells split into 4 haploid cells