Question

Protein A is a transcriptional regulatory protein for operon alpha. Gene expression of the operon is unregulated in the presence of co-factor molecule Q. If A is deleted, gene expression on the operon alpha is constitutive. What type of regulation is this and what type of regulatory/co-factor are A and Q?

Answer 1

Protein A is a repressor for the operon alpha. When protein A binds to the repressor the gene is turned off. So it is negative gene regulation.

Cofactor molecule Q might be binding to protein A preventing it from binding in to the repressor site thus making the gene transcription unregulated. There for the gene is not controlled and it leads to constitutive expression. Same goes with when gene A is deleted leading to the constitution expression of the gene

There fore type of gene regulation is negative.