#Question id: 800
#SCPH05 I Biotechnology
Following table lists the two major forms of DNA duplexes, conformation of base attached to the sugar and the nature of major and minor grooves.
|
DNA duplex |
Properties |
|
(A) A
form |
(i) Syn
conformation of the base to sugar |
|
(B) B
form |
(ii) Anti
conformation of the base to sugar |
|
|
(iii) Wide
major groove |
|
|
(iv)
Narrow major groove |
|
|
(v) Wide
minor groove |
|
|
(vi) Narrow
minor groove |
|
|
(vii) C-3’
endo sugar puckering |
|
|
(viii) C-2’
endo sugar puckering |
#Question id: 801
#SCPH05 I Biotechnology
Identify the type of DNA from the structures given below and match the correct form with its characteristics described.
#Question id: 802
#SCPH05 I Biotechnology
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 is a possible sequence and structure for this DNA molecule?
#Question id: 803
#SCPH05 I Biotechnology
A single-stranded DNA molecule contains 40 nucleotides and has the sequence 5’-(GA)20-3’. When this single strand binds to a complementary DNA strand to form a B-DNA structure,
#Question id: 804
#SCPH05 I Biotechnology
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
#SCPH05 I Biotechnology
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.