Cell Cycle

Question 1

Main stages of cell division

Answer 1

1. Nuclear division. There are two types of nuclear division- meiosis and mitosis. The nucleus divides into either two or four
2. Cell division. The whole cell divides into two or four daughter cells

Question 2

Semi conservative replication requirements

Answer 2

1. The four types of nucleotide must be present
2. Both strands of the DNA molecule must act as a template
3. The enzyme DNA polymerase is needed to catalyse the reaction
4. A source of chemical energy

Question 3

Meselsohn and Stahl Nitrogen experiment

Answer 3

Question 4

The four stages of Mitosis

Answer 4

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
5. (Interphase)

Question 5

Prophase

Answer 5

The chromosomes become visible and the nuclear envelope disappears

Question 6

Metaphase

Answer 6

The chromosomes arrange themselves in the centre of the cell and the spindle fibres form.

Question 7

Anaphase

Answer 7

The spindle fibres contract ad the chromatids are pulled towards the poles.

Question 8

Telophase

Answer 8

The chromatids reach the poles and stop being visible. The nuclear envelope and nucleolus reform and the spindles disintegrate.

Question 9

Interphase

Answer 9

The time when the cell is not dividing. Includes protein synthesis and DNA replication. There are three stages:

• Growth 1, when proteins are produced for organelle synthesis
• Synthesis, when DNA is replicated
• Growth 2, organelles grow and divide, and energy stores are increased

Question 10

Importance of mitosis

Answer 10

• Growth of a new organism after gamete fusion (haploid sperm and egg form a diploid cell)
• Differentiation of cells which then replicate to provide specialised tissues
• Repair of damaged cells/ replacing dead cells. It is important for the new cells to be exact copies of the originals.

Question 11

3 cell cycle stages

Answer 11

1. Interphase
2. Nuclear division
3. Cell division

Question 12

Cancer

Answer 12

• A group of diseases caused by a cellular growth disorder
• The result of damage to the DNA which regulates mitosis
• The abnormal cells develop forming a tumour which constantly expands in size

Question 13

Cancer treatment

Answer 13

• Prevents DNA from replicating
• Or, inhibits metphase by affecting spindle formation