Scientists investigated the cell cycle in Arabidopsis thaliana root tips. They measured the percentage of cells undergoing mitosis and DNA replication at different distances from the root cap.
Their results are shown in Table 1.
| Distance from root cap / μm\mu\text{m}μm | Percentage of cells undergoing mitosis | Percentage of cells undergoing DNA replication |
|---|---|---|
| 100 | 18.2 | 12.4 |
| 400 | 8.5 | 5.2 |
| 800 | 1.2 | 0.4 |
| 1500 | 0.0 | 0.0 |
Describe and explain the data in Table 1.
The scientists determined the percentage of cells undergoing DNA replication by using a chemical called BrdU. Cells use BrdU instead of nucleotides containing thymine during DNA replication.
Describe how BrdU would be incorporated into new DNA during semi-conservative replication.
Cells with BrdU in their DNA are detected using an anti-BrdU antibody with an enzyme attached.
Use your knowledge of the ELISA test to suggest and explain how the scientists identified the cells that have BrdU in their DNA.
