2. In the bacterium Bacillus sublilus, there are five genes coding for proline b
ID: 203168 • Letter: 2
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2. In the bacterium Bacillus sublilus, there are five genes coding for proline biosynthetic enzymes. They are located adjacent to one another on the chromosome. If excess pro present in the medium, the synthesis of all five enzyme the absence of pioline, ail live genes are coordinately expressed line is s is coordinately repressed, whereas in a. (1 point) Most imutations in this region of the chromosome result in the loss of activity of only one of the enzyniss. Explain how such a mutation would only effect the production of one enzyme. What is the counterpart of this type of mutation in the lac operon system? b. (1 point) Some mutations, mapping to one end of the cluster of proline biosynthesis genes, result in the loss of all five enzymes, even though none of the structural genes have been lost. Explain how such a mutation could affect all five genes. What is the counterpart of this type of mutation in the lac operon system? .Explanation / Answer
a) An operon is a set of genes consisting of a inhibitior gene (I) that codes for repressor (R), a promoter (P) the binding site of RNA pol for transcription initiation, an operator (O) the binding site of active repressor protein for transcription termination, and structural genes that codes for a functional peptide.
If the inhibitor is mutation, then it loses its capability of binding to operator causing the transcription to stay ON, constitutive transcription.
Mutation in operator inhibits the binding of repressor protein to the operator, causing the transcription to stay ON, constitutive transcription.
a) Mutation in one of the structural genes, inhibits the formation of the mutant structural gene. For example - In Lac operon if lac Y gene is mutated then only its transcription will be terminated and lac Z and lac A gene will be transcribed.
b) Mutation in promoter alters the binding of RNA pol causing the transcription to switch OFF and therefore transcription of structural genes is inhibited.
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