Cell cycle & Mitosis

Question 1

What do all multicellular, eukaryotic organisms require?

Answer 1

• A continuous supply of new cells

Question 2

What can the continuous new cells in multicellular, eukaryotic organisms be used for?

Answer 2

• Growth
• Development
• Repair
• These occur particularly in young organisms who need to grow in size.
• It also occurs in older organisms who must constantly replace lost cells e.g: the skin cells which continuously fall off our bodies

Question 3

What is the cell cycle?

Answer 3

The process which new cells are generated.
(The life cycle of the cell)

Question 4

What are the 3 main stages within the cell cycle?

Answer 4

• Growth
• DNA replication & mitosis
• Division

Question 5

What is interphase?

Answer 5

• The first stage of the cell cycle, during which the cell grows and replicates its DNA in preparation for division.

Question 6

Steps of the cell cycle:

Answer 6

1. The cell grows in size and increases the number of subcellular structures it contains. E.g: mitochondria, ribosomes (Interphase)
2. The DNA is duplicated so that the two new cells will have a full set of DNA. (Interphase)
3. As the cell continues to prepare for division, it duplicates each of the 46 chromosomes.
   - The duplicate stays attached to the original chromosome that it was copied from so together form an ‘X’ shape. (Interphase)
4. Once the cell is ready to divide, all 46 of the cells chromosomes line up along the centre of the cell. (Mitosis)
5. Cell Fibres from either side of the cell attach to the respective half of the chromosome.
   - The cell fibres pull the arms of the chromosome to opposite side of cell (poles), breaking the chromosomes into 2 separate arms. (Mitosis)
6. Now that all the genetic material has been divided to either of the sides of the cell, the final stage occurs.
   - The cell membrane and cytoplasm pull apart forming 2 identical daughter cells. (Division)
7. These contribute to growth development and repair and can undergo the cell cycle all over again.

Question 7

What happens whilst a cell is NOT dividing? (Going about its normal functions).

Answer 7

• The DNA is spread out in long strings

Question 8

How does the cell prepare for division?

Answer 8

• The long strings of DNA condenses into chromosomes.

Question 9

What is interphase?

Answer 9

• The first stage of the cell cycle, during which the cell grows and replicates its DNA in preparation for division.