mitosis

Question 1

1. What does mitosis do?

Answer 1

Mitosis is the division of the nucleus. Mitosis is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication

Question 2

2. Which cells can divide in multicellular organisms?

Answer 2

Not all cells divide in multicellular organisms. Some cells retain the ability to divide and show a cell cycle.

Question 3

3. When does DNA replication occur in the cell cycle?

Answer 3

During interphase. It occurs during the S-phase of interphase.

Question 4

4. What is the role of spindle fibres in mitosis?

Answer 4

The spindle fibres attach to the centromeres of the chromosomes; The spindle fibres shorten, which leads to the separation of centromeres and moves chromatids to opposite poles of the cell.

Question 5

5. What is the role of the centromere in mitosis?

Answer 5

Holds chromatids together; Attaches chromatids to spindle; Allows chromatids to be move to opposite poles when the centromere splits

Question 6

5. What is cytokinesis?

Answer 6

Division of the cytoplasm and formation of a new cell membrane between the cells.

Question 7

6. What is the cell cycle? Describe each stage.

Answer 7

Eukaryotic cells that retain the ability to divide show a cell cycle which consists of: interphase, mitosis then cytokinesis. G1- cell grows and forms new organelle and proteins S-DNA replication occurs G2-Cell continues to grow and makes proteins needed for cell division. DNA is checked for errors (mutations). Mitosis- division of the nucleus

Question 8

7. Draw and describe the behaviour of chromosomes during interphase.

Answer 8

A period of cellular activity, increasing the size of cytoplasm and number of organelles. DNA is replicated, but not condensed into visible chromosomes.

Question 9

8. Draw and describe the behaviour of chromosomes and the cell during prophase.

Answer 9

Chromosomes condense, thicken and become visible. They appear as two sister chromatids held together by a centromere. The centrioles migrate to the opposite poles of the cell and form spindle fibres. The nuclear envelope disapears

Question 10

9. Draw and describe the behaviour of chromosomes and the cell during metaphase.

Answer 10

All the chromosomes line up on the equator of the cell; Chromosomes are attached to spindle fibres; By their centromere;

Question 11

10. Draw and describe the behaviour of chromosomes and the cell during anaphase.

Answer 11

The spindle fibres contract and the centromere divides; chromatids are pulled to opposite poles of the cell;

Question 12

11. Draw and describe the behaviour of chromosomes and the cell during telophase

Answer 12

Chromosomes uncoil and become longer, thinner. The nuclear membranes begin to form around the daughter nuclei, cytokinesis begins.

Question 13

12. Explain how to calculate the mitotic index

Answer 13

The number of cells in mitosis ÷total number of cells. The answer should be a decimal.

Question 14

13. Explain how to calculate the number of cells that there will be after a period of time undergoing cell division

Answer 14

2n x the starting number of cells N = the number of times cell division has occurred. This can be found out by multiplying the mitotic index by the total time period (to find the proportion of time cells are in mitosis) OR you may be given the length of the cell cycle and can then divide the total period of time by the length of one cell cycle.