The diagram shows cells taken from a skin wound on two different days after a cyclist fell from a bicycle. On day 1, the edges of the wound are far apart. O...
Question 1 Report
The diagram shows cells taken from a skin wound on two different days after a cyclist fell from a bicycle. On day 1, the edges of the wound are far apart. On day 7, many more skin cells have formed and the gap is smaller. The cells at the wound edge are dividing by mitosis.
(a) Describe the change shown in the diagram between day 1 and day 7. [2]
(b) Explain how mitosis produces cells that can replace damaged skin cells. [4]
(c) State two structures that both the original skin cell and each new skin cell contain. [2]
(d) Which stage of the cell cycle includes copying of DNA? [1]
(e) Suggest why uncontrolled mitosis can be harmful to the human body. [2]
Answer Details
(a) By day 7 there are more skin cells, and the wound gap is smaller or partly filled by cells. [2 marks] Mitosis increases cell number, allowing cells to spread into the damaged area.
(b) Before the cell divides, its DNA, and therefore its chromosomes, are copied. The copied chromosomes are then separated equally into two cells. This produces two daughter cells, each with the same chromosome number and genetic information as the original skin cell. These genetically identical cells can function as replacement skin cells. [4 marks]
(c) Each original and new skin cell contains any two of: cell membrane, cytoplasm, nucleus, mitochondria, chromosomes or DNA. [2 marks] For example, both contain a cell membrane and cytoplasm.
(d) DNA is copied during interphase. [1 mark] This happens before mitosis begins.
(e) Uncontrolled mitosis can form a tumour. The tumour can disrupt normal tissues or stop an organ working properly. [2 marks]
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