Plant Mitosis

Be able to identify cells in interphase, prophase, metaphase, anaphase, telophase.

Time Length for the Stages of Mitosis p. 92

Table 1 - Proportion of Cells in Each Stage of Onion Root Tip Mitosis
Should be able to see ~100 cells under high power; interphase is usually longest, metaphase/anaphase shortest.

Stage	Trial #1	Trial #2	Trial #3	Total #	%
1. Interphase	75	90	75	240	80
2. Prophase	12	8	10	30	10
3. Metaphase	0	2	4	6	2
4. Anaphase	3	3	3	9	3
5. Telophase	8	3	4	15	5
Total #	98	106	96	300	100

Animal Mitosis p. 93

Be able to identify cells in a whitefish blastula.

Questions p. 94

1. A human has a diploid (2N) number of 46. Why are the chromosomes paired? Where did each set originate?

   One set originates from each parent - father and mother.

2. Rank the stages of mitosis in order from the longest to the shortest based on your calculations. Give the number of minutes for each stage.

   Interphase is usually longest, followed by prophase and telophase; metaphase/anaphase is usually shortest.
   See p. 86: Onion root tip cells take 960 minutes (16 hours) to complete the cell cycle.

   If interphase comprises 80% of mitosis: 960 min. * 80% = 768 min. (12 hours, 48 min.)
   prophase: 960 min. * 10% = 96 min.
   metaphase: 960 min. * 2% = 19 min.
   anaphase : 960 min. * 3% = 29 min.
   telophase/cytokinesis: 960 min. * 5% = 48 min.

3. Why can we assume that the most common (numerous) stage takes the longest amount of time.

   The cells observed should be in random positions of the cell cycle, so the longer a stage takes, the more cells we should see.

4. Compare and contrast mitosis in plant cells and animal cells.

   The stages are similar, but animal cells form a furrow in telophase/cytokinesis (see p. 87).

Drawings/photos of pipe cleaners to simulate the stages of meiosis.

Questions p. 98

1. Are the 2 products of Meiosis I diploid or haploid?

   Haploid - Meiosis I is the reduction division.

2. Describe how the 4 daughter cells produced in meiosis are different from each other and from the starting cell.
   • The daughter cells are haploid instead of diploid, and have undergone genetic recombination due to crossing over in prophase I.
   • Due to different orientations of tetrads in metaphase I, the 4 daughter cells are genetically different from each other.

3. Compare and contrast the 4 daughter cells produced at the end of Telophase II in your first and second trials.

   The daughter cells should have different combinations of paternal and maternal chromosomes inherited from the diploid starting cell.