5) A mutation in E. coli designated polA1 was discovered that is deficient in DNA polyermase...

5) A mutation in E. coli designated polA1 was discovered that is deficient in DNA polyermase I activity Because of this, researchers hypothesized that DNA duplication may not be successful. Is their hypothesis true? If it was not, why? In what other way could this strain be deficient?

Expert Solution

The hypothesis is false. This is because DNA polymerase I in E. coli exhibits functions like follows:

DNA pol I acts as a 5'?3' DNA-Dependent DNA polymerase activity that requires a 3' primer site and a template strand. DNA pol I also exhibits 3'?5' exonuclease activity or proofreading. It is also involved in 5'?3' exonuclease activity mediating nick translation during DNA repair. DNA polymerase I acts as a 5'?3' RNA-dependent DNA polymerase activity. The efficiency of Pol I on RNA templates is low and is about only 0.1–0.4% which is less than its efficiency on DNA templates.

Though multiple functions are carried out by DNA polymerase I, the actual function of it was discovered by an experiment creating mutation in deficient Pol I mutant strain of E. coli. The mutant strain was isolated and treated with a mutagen. These mutant E. coli strains that lack Pol I enzyme formed colonies. By this it was evident that DNA pol I is not required DNA replication. Moreover, the mutant strains lacking pol I exhibited extreme sensitivity to DNA damage by UV light. By this it is evident that, DNA polymerase I is mostly involved in DNA repair mechanism rather than in DNA replication.

gladiator answered 2 years ago

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