(10 pts) You have made an interesting observation concerning overexpression of p
ID: 276733 • Letter: #
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(10 pts) You have made an interesting observation concerning overexpression of phage ? int gene. In lab, you made a plasmid construct that placed the int gene downstream of a regulatable promoter and supplied a strong ribosome binding site for the mRNA transcript encoding int. When int expression was turned on from this construct, protein synthesis was inhibited and cells died. However, cell death was not due to toxicity of the Int protein produced because the harmful effects of int overexpression is reversed if cells contain a plasmid expressing an arginyl tRNA gene, which makes a tRNA that decodes the AGA codon 1. You also noticed this pattern of usage of arginine codons in the Int protein (shown in table below) Codon Number of codons Frequency of usage in in int CGU CGC CGA CGG AGA AGG E. coli proteins 0.42 0.37 0.05 0.08 0.04 0.03 6 10 9 From the information provided, what do the results suggest about the mechanism of overexpression toxicity? Answer 75 words maximumExplanation / Answer
The given table suggests that the ‘int’ protein contains 10 AGA codons. When the cell is able to make a tRNA that could decode this AGA codon, the harmful effects are reversed.
If the tRNA is not present, i.e, if the mRNA is not getting translated into protein, then cell death is observed. In the presence of arginyl tRNA, the mRNA is getting translated into protein and hence survival.
Therefore, the ‘int’ protein is required for the cell survival.
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