Concept explainers
DNA polymerase I (Pol I) of E. coli consists of three functional parts (domains): an N-terminal domain with 5' to 3' exonuclease activity required for removal of the RNA primer, a central domain responsible for 3' to 5' exonuclease proofreading, and a C-terminal domain with polymerase activity. Pol I is thought to simultaneously remove RNA primers and fill in the gaps that result (figure 13.14). A group of proteins known as RNaseH also have 5' to 3' exonuclease activity and can thus remove RNA primers. However, they lack the other two functions observed for Pol 1. Predict the ability of the following mutants to replicate DNA: (1) a strain with a mutant gene encoding Pol I such that it no longer has polymerase activity (but retains both types of nuclease activities); (2) a strain without RNaseH proteins; (3) a strain with a mutant gene encoding Pol I such that it no longer has 5' to 3' exonuclease activity (but retains 3' to 5' nuclease and polymerase activities); (4) a strain with the mutant Pol I described in (3) and a strain lacking all RNaseH proteins. Explain your reasoning for each.
Read the original paper: Fukushima, S., et al. 2008. Reassessment of the in vivo functions of DNA polymerase I and RNaseH in bacterial cell growth. J. Bacteriol. 189:8575.
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Prescott's Microbiology
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- Using the numbered sites on the DNA double helix strands below, where would the DNA Primer ACTTGCGA bind to for DNA Amplification?arrow_forwardin the human gene for the beta chain of hemoglobin, the first 30 nucleotides in the amino acid coding region is represented by the sequence 3'TACCACGTGGACTGAGGACTCCTCTTCAGA-5'. What is the sequence of the partner strand? If the DNA duplex for the beta chain of hemoglobin above were transcribed from left to right, deduce the base sequence of the RNA in this coding region.arrow_forwardDNA Polymerase Holoenzyme IIlI is represented below. It consists of several domains with distinct functions. The structure capable of 5' to 3' DNA polymerization is represented by the letter and the structure capable of 3' to 5' exonuclease activity is represented by the letter B. -D DNA Pol II holoenzyme D; A А; С А;B А А; D В; D O Oarrow_forward
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