Ap Bio Lab 3- Mitosis and Meiosis

By: Petrell Vereen

2/5/12

Analysis Questions:

1. Mitosis leads to 2 daughter cells by first duplicating its DNA, then separating the DNA and giving identical sets of information to each daughter cell by separating the tetrads. During interphase, the cell does all of its functions for the organism, in between the times that it is replicating.

2. Mitosis in plant and animal cells differ because of the cell wall in plants that isn’t present in animals. The cell wall does not break apart, but instead another cell wall is formed in the middle of the cell undergoing the replication at the metaphase plate that serves as the place where the two daughter cells are defined.

3. The centrosome regulates the cell cycle and its progression. It also serves as the places where the microtubules that are used during mitosis are organized. The centrosome doesn’t have to be used however, because a cell can divide without the centrosome.

Table 3.1: Time for Cell Replication

Number of CellsPercent of Total Cells

CountedTime in Each Stage

Field 1 Field 2 Field 3 Total

Interphase 45 38 52 135 67.50% 16h 12min

Prophase 5 11 9 31 15.50% 3h 43min

Metaphase 2 4 3 14 7.00% 1h 41min

Anaphase 1 2 3 11 5.50% 1h 19min

Telophase 1 3 2 9 4.50% 1h 5min

Total cells Counted200

Questions:

1. If the area of the root tip was not observed, and another area was instead observed, then there would less division because the other parts of the onion would have more cells in interphase that are doing their function, while the cells on the root tip are dividing rapidly to grow.

2. Most of the time spent in mitosis is spent in the Prophase part of division. The next highest time is spent in metaphase, then anaphase, then finally Telophase.

Analysis and Investigation:

1. Mitosis includes the nucleus dividing once, while in meiosis, the nucleus divides twice. Crossing over only occurs in meiosis. There are 4 daughter cells that result from meiosis, while only 2 result from mitosis.

2. Table 3.2:

  Mitosis Meiosis

Chromosome number of parent cells 2n 2n

Number of DNA replications 1 1

Number of divisions 1 2

Number of daughter cells produced 2 4

Chromosome number of daughter cells

2n n

PurposeGrowth, replacement

of cellsGametogenesis

3. In Meiosis I, the tetrads separate, while in Meiosis II, the sister chromatids separate.

4. Oogenesis produces 1 polar body, and 1 egg cell, while spermatogenesis forms 4 daughter sperm cells.

5. Meiosis allows the chromosome number to reach 1n, which allows two cells to fuse and create a new cell that replicates with the information from 2 parents. The creation of the 1n cells allow for crossing over to occur and create variation in the offspring.

Table 3.3: Sordaria

Number of 4:4 Number of Asci Showing Crossover

Total Asci % Asci Showing Crossover Divided by

2

Gene to Centromere

Distance (Map Units)

29 21 50 21.00 21.00

 

Crossing over in Meiosis – 2:4:2