Question

Several enzymes are required for the biosynthesis of the aromatic amino acids tyrosine and phenylalanine. The genes aroFand aroL, located in two separate operons, encode two of the enzymes needed to make tyrosine.Expression of aroF and arol is controlled by a "TYRosine Repressor" protein called tyrR that can bind to tyrosine. How would expression of aroF and arol change in cells with a mutation that inactivated the tyrR gene? Do you expect that the tyrR protein binds to DNA better when it is bound to B. tyrosine, or when it's not bound? What is the term for the DNA sequence where tyrR binds? C. You identify a consensus binding site for tyrR, listed below, along with the tyrR binding sites that regulate the aroF and arol genes. consensus TGTAAA (N6) TTTACA cnsensus TGTAAA (N6) TTTACA cGaAtACTTAtg TGCAAATTgACAaroL aroF What is the relative affinity of tyrR for the binding sites in the aroF and arol D. genes? Circle one option tyrR binds with higher affinity to aroF than arol tyrR binds with the same affinity to aroFand arol tyrR binds with lower affinity to aroFthan aroL At intermediate levels of tyrosine, only a fraction of tyrR protein binds to DNA. E. How do you think this affects tyrR binding at aroF versus aroL? What is the effect of intermediate levels of tyrosine on aroF versus arol expression?

Answer 1

A) Mutation in tyrR gene will inactivate the gene and so the protein produce will inefficiently repress aroF and aroL genes as compared to wild type tyrR gene.

B) When tyr protein is bound to tyrosine, it cannot bind efficiently to DNA.

C) Its promoter site.