Table 1 shows the chromosome number counted in cells taken from a culture of human skin cells. The culture was allowed to grow after a small wound had been ...
Question 1 Report
Table 1 shows the chromosome number counted in cells taken from a culture of human skin cells. The culture was allowed to grow after a small wound had been made in the cell layer. Fig. 1 shows chromosomes in one cell from the culture at a stage of mitosis. A cap was used to keep the culture dish sterile while cells divided.
| Type of cell in the culture | Number of chromosomes in one cell |
|---|---|
| cell before mitosis | 46 |
| one cell immediately after mitosis | 46 |
| cell after DNA replication but before division | 46 |
(a) Complete the statement: chromosomes are structures made from DNA and __________. [1]
(b) Use Table 1 to state the number of chromosomes in each new human cell produced by mitosis. [1]
(c) Describe what is shown by label Q in Fig. 1. [2]
(d) Explain why mitosis is needed when the wounded cell layer repairs. [2]
Answer Details
(a) Chromosomes are structures made from DNA and protein. [1]
(b) Each new human cell produced by mitosis contains 46 chromosomes. Mitosis preserves the chromosome number of the original body cell. [1]
(c) Label Q shows a pair of identical chromatids, which are copies of one chromosome. The chromatids are joined at a centromere. [2]
(d) Mitosis produces more cells. At a wound, these new skin cells replace damaged or lost cells and help close the gap in the cell layer. [2]
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