The effector molecule that binds to the activator of the lac operon is:
A. lactose.
B. glucose.
C. cAMP.
D. allolactose.
Which of the following is notusually involved in the processing of primary mRNA transcripts?
A. addition of multiple adenosines to the 3' end
B. covalent joining of exons
C. methylation of nucleotides at the 5' end
D. insertion of intron sequences
The binding of tryptophan to the Trp repressor protein results in:
A. the dissociation of the repressor from the operator sequence.
B. a conformational change in the repressor that allows the repressor to bind the operator.
C. the recruitment of RNA polymerase.
D. an increase in the expression of tryptophan biosynthetic enzymes.
Riboswitches are alternative RNA structures mediated by the binding of molecules to the RNA. One example of a riboswitch is the intrinsic terminator hairpin (stem-loop) structure that may form in specific sites of newly transcribed RNA.
This stable RNA hairpin, if followed by 48 uridine residues at the 3' end, is a signal for transcriptional termination of that RNA. The termination of transcription involves interactions of the RNA polymerase, the hairpin, and the template strand sequence. RNA polymerase reads the DNA template strand 3' to 5' while synthesizing the new (nascent) RNA strand 5' to 3'. Which of the following DNA sequences, when transcribed, will most likely form an intrinsic transcription termination RNA structure?
A. 3' AAAAAAUUUUUU TTTTT 5'
B. 3' ACCCCCATGGGGGAAAAAA 5'
C. 3' GGGGGGTTTCCCCCTTTTTT 5'
D. 3' ACGACCCGGACGGGGGGG 5'
E.3' TTTTTTCCCCCCAAAGGGGGG 5'
The activator for the lac operon is:
A. CRP.
B. cAMP.
C. lactose.
D. allolactose.
Quick Reply
