Wild-type E. coli grow best at 37°C but can grow efficiently up t...

Question

Wild-type E. coli grow best at 37°C but can grow efficiently up to 42°C. An E. coli strain has a mutation of the sigma subunit that results in an RNA polymerase holoenzyme that is stable and transcribes at wild-type levels at 37°C. The mutant holoenzyme is progressively destabilized as the temperature is raised, and it completely denatures and ceases to carry out transcription at 42°C. Relative to wild-type growth, characterize the ability of the mutant strain to carry out transcription at

What term best characterizes the type of mutation exhibited by the mutant bacterial strain? (Hint: The term was used in Chapter 4 to describe the Himalayan allele of the mammalian C gene.)

Accepted Answer

Hey, everyone. Let's take a look at this question together R P O D mutation results in a single amino acid substitution in the Sigma subunit of R N A polymerase. This substitution affects the binding specificity of R N A polymerase. Two promoters causing it to preferentially recognize certain promoters over over others. Identify the type of mutation represented by this substitution. Is it answer choice. A knockout mutation, answer choice B missense mutation, answer choice, C, silent mutation or answer choice D promoter mutation. Let's work this problem out together to try to figure out what type of mutation is represented by the substitution in the R P O D mutation. So we have this mutation in R P O D resulting in a single amino acid substitution where we have glutamic acid to lysine in the sigma 70 subunit of R N A polymerase. So we have a substitution of a single, I mean no acid. And we also know that the codons that code for glutamic acid R A A G or G A G and lysine is coded by the codons AAA or A A G. And we're able to see that glutamic acid and lysine differ by one nucleotide, which means that the substitution of a single amino acid is the result of a substitution of a single nucleotide. Which means that the type of mutation that we have here is a point mutation. Specifically a type of point mutation called a miss sense mutation, which a mis sense mutation is a type of point mutation caused by a change of a single nucleotide resulting in that substitution of a single amino acid. So that means that the type of mutation represented by this substitution is answer choice B missense mutation. The correct answer since we know that the R P O D mutation results in a single amino acid substitution in which we have glutamic acid being changed for lysine. And glutamic acid is coated by either the codons A A G or G A G and lysine is coated by the codons AAA or A A G which they have one different nucleotide between the two. So the change from glutamic acid to lysine is the result of a change in a single nucleotide leading to the change of a single amino acid in the protein product, which means that we have a point mutation specifically called a missense mutation, which is answer choice B. The correct answer. I hope you found this video to be helpful. Thank you and goodbye.

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