Describe5 marksChallenge
A researcher cultured human fibroblasts and measured the average telomere length and the proportion of cells in different phases of the cell cycle after several population doublings. The data are shown in the table below.
| Passage number | Average telomere length (bp) | Percentage of cells in G1 | Percentage of cells in S phase | Percentage of cells in G2/M |
|---|---|---|---|---|
| 5 | 8500 | 55 | 30 | 15 |
| 20 | 7200 | 60 | 25 | 15 |
| 40 | 5500 | 75 | 10 | 15 |
| 60 | 4000 | 85 | 5 | 10 |
Describe the structure of a chromosome, the main events of the mitotic cell cycle, and the role of telomeres in preventing loss of genes from chromosome ends during replication. Using the data, describe the relationship between telomere length and the proportion of cells in S phase, and describe how this limits the ability of normal somatic cells to divide repeatedly.