#Question id: 804
#Unit 1. Molecules and their Interaction Relevant to Biology
With respect to microRNAs, which, if any, of the following statements, is false?
a) A microRNA normally works by binding to perfectly complementary sequences within an RNA transcript, usually an mRNA.
b) Like the great majority of mRNAs an miRNA is usually produced as a larger precursor RNA that is capped and has a 3’ poly(A) tail.
c) The precursor miRNA undergoes different types of post-transcriptional cleavage by endoribonucleases that are specific for double-stranded target sequences.
d) A nuclear endoribonuclease called dicer cleaves the miRNA precursor so that it forms a stem-loop RNA.
#Question id: 805
#Unit 1. Molecules and their Interaction Relevant to Biology
miRNAs are encoded in the genome as segments of longer transcripts. Their characteristic structure helps identify them and predict the target genes they might regulate. Which of the following are the characteristic features of these small RNA molecules?
I. The functional form of an miRNA is typically 21 or 22 nucleotides (it can vary from 19 to 25 nucleotides).
II. The first cleavage liberates the stem-loop, called the pre-miRNA; the second generates the mature miRNA from the pre-miRNA.
III. The pre-miRNAs can be encoded by any part of a transcript: that is, they might fall within coding regions, within leader regions, or within Introns.
IV. The base pairing between miRNA and target RNA is initiated by interactions of so-called seed residues—the sequence between bases 2 and 9 of the 22-nucleotide miRNA.
#Question id: 806
#Unit 1. Molecules and their Interaction Relevant to Biology
A single-stranded DNA molecule contains 40 nucleotides with equal amounts of A, C, G, and T. This DNA strand can combine with a complementary DNA strand to form a double-stranded DNA molecule. Which characteristic does this double-stranded molecule have when it forms a B-DNA structure?
#Question id: 807
#Unit 1. Molecules and their Interaction Relevant to Biology
Which of the following forces can stabilize a normal DNA double-helix?
#Question id: 808
#Unit 1. Molecules and their Interaction Relevant to Biology
Which, if any, of the following statements is false?
#Question id: 809
#Unit 1. Molecules and their Interaction Relevant to Biology
A single-stranded DNA molecule contains 40 nucleotides with equal amounts of A, C, G, and T. This DNA strand can combine with a complementary DNA strand to form a double-stranded DNA molecule. Which of the following double-stranded DNA molecules would denature at a lower temperature than the 40 base-pair double-stranded molecule described above?