Cell Division (1.6)

Question 1

What are the two types of cell division?

Answer 1

Mitosis: The division of the nucleus into two genetically identical daughter nuclei. Occurs in all cells.
Miosis: Cell division for the production of gametes (sex cells). Occurs in the ovaries and testes.

Question 2

The Cell Cycle

Answer 2

The series of events that take place in a cell leading to its division and replication. Includes mitosis and cell growth.

Question 3

What stage precedes mitosis?

Answer 3

Interphase - DNA is present as uncondensed chromatin in a nucleus. Centrosomes and other organelles are duplicated.

Question 4

First stage of mitosis

Answer 4

Prophase - DNA supercoils and condenses into chromosomes. Chromosomes are made up of genetically identical sister chromatids joined at a centromere. The nuclear membrane breaks down and dissolves.

Question 5

Second stage of Mitosis

Answer 5

Metaphase - Microtubule spindle fibres from the centrosomes connect to the centromere of each chromosome causing the chromosomes to align along the centre of the cell.

Question 6

Third stage of Mitosis

Answer 6

Anaphase - The chromosomes segregate, pulling the chromatids apart. Move to opposite poles of the cell.

Question 7

Last stage of Mitosis

Answer 7

Telophase - Spindle fibres dissolve. Chromosomes decondense, nuclear membranes reform. Cytokinesis occurs, splitting the cell into two nuclei.

Question 8

Stage after Mitosis

Answer 8

Cytokinesis - Division of the cytoplasm. The cell splits in two.

Question 9

Cytokinesis differences in plant and animal cells

Answer 9

Animal cells don’t have a cell wall so in cytokinesis a cleavage furrow is formed instead of a cell plate.

Question 10

Mitotic Index

Answer 10

Mitotic Index = number of cells in mitosis/total number of cells x 100

Question 11

Stages of the Cell Cycle

Answer 11

G1 - Period of cell growth. Interphase begins.
S - Period where the DNA is replicated (Interphase)
G2 - Period after DNA has been replicated. (End of Interphase).
Mitosis - Prophase, Metaphase, Anaphase, Telophase. Nuclear division.
Cytokinesis - Cytoplasm divides, forming two separate cells.

Question 12

What are Cyclins?

Answer 12

Cyclins are chemicals that signal the beginning and end of different stages in the cell cycle. They do this by undergoing periods of chemical synthesis and by activating cyclin-dependent kinases (CDKs) which control cell processes by phosphorylation.

Question 13

Metastatic cancer

Answer 13

Where cancerous cells spread into other surrounding tissues and travel to other parts of the body, producing new tumours.

Question 14

What is a tumour?

Answer 14

A tumour is a group of cells that has formed as a result of uncontrolled cell division and growth.

Question 15

Oncogenes

Answer 15

Oncogenes code for proteins that promote cell growth and the cell cycle. When oncogenes mutate they become cancer causing as they accelerate cell division.

Question 16

Tumour suppressor genes

Answer 16

Tumour suppressor genes code for proteins that promote cell apoptosis and repress the cell cycle. Their normal function prevents cancer so they are sometimes referred to as anti-oncogenes. If both copies in the cell fail to work, cancer may occur.