Question 1
Multiple choiceMedium1 markBacteriophage lambda is undergoing its lytic cycle in bacterial cells. The table shows mean measurements at successive times after infection, all normalized per initially infected bacterium.
| Time after infection / min | Phage DNA copies per initially infected bacterium | Assembled phages inside bacteria | Free infectious phages |
|---|---|---|---|
| 0 | 1 | 0 | 0 |
| 10 | 28 | 0 | 0 |
| 20 | 28 | 20 | 0 |
| 30 | 28 | 0 | 18 |
Which interval is most consistent with release of assembled phages from the bacteria?
Show answer and explanation
Answer: B. From 20 to 30 min, assembled phages inside bacteria fall from 20 to 0 while free infectious phages rise from 0 to 18. This indicates release; the phage DNA copy number remains unchanged during this interval.
A: selects the earlier increase in phage DNA, which indicates replication rather than release.
C: identifies the interval when assembled particles appear inside bacteria, indicating assembly before release.
D: assigns replication to an interval when the phage DNA copy number is unchanged.
Remember: distinguish replication, assembly and release by tracking what changes inside and outside the host cell.