1) The E. coli gene lacYencodes a protein called lactose permease, needed for di
ID: 4660 • Letter: 1
Question
1) The E. coli gene lacYencodes a protein called lactose permease, needed for digestion oflactose. A mutation in this gene at codon 64 changed the normalglycine codon into a valine codon. The mutant protein isnon-functional. However, function is restored by a second mutationthat changes codon 50 from an alanine codon to a threonine codon.Are the following terms appropriate or inappropriate to describethis second mutation? Briefly explain each answer.
a. Reversion
b. Intragenic suppressor
c. Intergenic suppressor
Explanation / Answer
A mutation in a gene at64th position which converted Glycine toValine in afunctional protein is a primary mutation. A second mutation in thishas caused the restoration of the original functionof the protein. In the below termsthe term that is most appropriate is intragenicsuppressor. Intragenic suppression isdue to the secondmutation which corrects the functioning of the mutant genewithin the same gene at a differentposition. As the lacY gene hasbecome functional due to a mutation at a different position, thisterm appropriate. Reversion mutation iscaused due to the secondmutation at the samesite of the first mutation to restore the function of the original. Reversion mutation is thecorrection of the mutationat the same site. In this above lac Y geneas the mutation is at two different positions, this term is notappropriate. Intergenic suppression is due tothe second mutation that results from a mutation of a differentgene. The product of thismutation compensates for the dysfunction of the first. In the given one(lacY) as only one gene is considered and as more genes are notinvolved this term is also not appropriate. Missense mutation is dueto the singlenucleotide change which results in a different amino aicdsthat caused the resulting protein to benon-functional. This is true when the64th position of the codon is mutated, but as a secondmutation has not occurred at the same position and has occurredat 50th position this term will not be applicable. Hence, the mostappropriate term for this lacY gene mutation is intragenicsuppressor.Related Questions
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