An operon has four protein‐coding genes (for proteins A, B, C, D). Which proteins will be produced (a) if the promoter ahead of gene A is mutated? (b) if the stop codon of gene B is deleted; (c) if a repressor binds to the operator (regulatory DNA) for this operon.

Question

An operon has four protein‐coding genes (for proteins A, B, C, D). Which proteins will be produced   (a) if the promoter ahead of gene A is mutated?  (b) if the stop codon of gene B is deleted;  (c) if a repressor binds to the operator (regulatory DNA) for this operon.

anonymous · Answer

you didn't give a schematic view of said operon along, o I suppose you don't have it. this means, one operator, the 4 genes are directly consecutive, no additional operator inbetween.

(a) a mutation can mean anything. most of the time, it means that the operator will be silenced, so no protein expression at all. but in some cases, an eventual repressor won't be able to bind -> your genes will all be expressed in a greater rate.

(b) I suppose, the stop codon is on the protein level? well, here we have got many options, too. most of the time, a non-functional conglomerate of proteins B and C is produced. I'll leave it with that. =)

(c) if a repressor binds, no protein will be made.

matt101 · Answer

I agree with Schleifspur. And a schematic view would be helpful...