Please help! b. A large number of temperature-sensitive DNA replication mutants
ID: 144093 • Letter: P
Question
Please help!
b. A large number of temperature-sensitive DNA replication mutants have been isolated from a bacterium. The mutants are unable to replicate DNA at 42°C but can do so at 30°C. If the bacteria are grown at 30°C for several generations and, then the temperature is raised to 42°C, two categories of mutants can be distinguished, referred to as quick stop and slow-stop. Quick-stop mutants stop replicating DNA immediately once the temperature is raised. Slow-stop mutants replicate DNA for a few more minutes after the temperature is raised and then stop. Give one example, with a brief justification, of a specific cell component that could be disabled in a quick-stop mutant and another similarly justified example of a component that is defective in a slow-stop mutant.Explanation / Answer
1. quick stop mutants are defective in components of replication apparatus especially enzymes needed for elongation.
ex: temperature sensitive mutants of DNA topoisomerase which are unable to relieve winding tension ahead of replication fork.
2. slow stop mutants are defective in events involved in initiating a cycle of replication.
ex: in E.coli temperature sensitive mutants are visible at 99mins which obstruct initiation of replication .