1. Which of the following mRNA will not be polyadenylated?
a) Actin mRNA
b) Receptor mRNA
c) Canonical histone mRNA
d) Transport channel mRNA
Explanation: Most of the mRNAs are polyadenylated except the major histone mRNAs. These are the canonical mRNA that need a rapid turnover and have a unique 3’ end. However, the non-canonical mRNA produced during S phase are polyadenylated
2. Which of the box is retained in mature mRNA?
a) TATA box
b) Pribnow box
c) G/U box
d) AU box
Explanation: The TATA box and Pribnow box are part of the promoter so they are not even transcribed into RNA. The GU box on the other hand is cleaved off during polyadenylation while the AU box is retained even after polyadenylation.
3. Which of these sequences will mark a site of polyadenylation?
a) AAUAAA—-GGUUUGU——-CA——-
b) UUUGUGUG—–CA—-AUUAAA
c) AAUAAA—–CA—-UUUUGUGU
d) CA—–AAUAAA——UUUUGUGUGU
Explanation: The cleavage sequence has a consensus of AAUAAA sequence towards the 5’ and a G/U box towards the 3’ end and a CA dinucleotide in the middle. The cleavage is just after 3’ to the CA.
4. Which of the following does not directly interact with DNA?
a) CPSF
b) CStF
c) PABPII
d) PAP
Explanation: PAP binds to CPSF and CStF by protein-protein interaction and doesn’t actually bind to the DNA. However, the other factors are cis elements binding to specific sequences.
5. CPSF and CStF bind to ____________
a) AAUAAA and G/U box respectively and bind is very strong
b) G/U box and AAUAAA respectively and bind is very strong
c) G/U box strongly but weakly AAUAAA
d) AAUAAA weakly but stabilization occurs after G/U binding
Explanation: CPSF binds to AAUAAA but the interaction is weak. This interaction is strengthened by CStF binding to G/U box and further stabilization occurs at CFI and CFII binding.
6. PAP has a processivity of ___________
a) 5-10 bases
b) 10-20 bases
c) 50-100 bases
d) 100-250 bases
Explanation: PAP has a very low processivity of about 10-20 A bases before binding of PABP II which has a very high processivity of 100 to 250 poly A bases.
7. Which experimental method can you use to detect 3’ end processing?
a) CHIP
b) Affinity chromatography
c) Northern blot
d) Immunofluorescence
Explanation: An affinity chromatography using oligo T sephadex beads in the column can be used to detect proper 3’ processing. If the RNA is properly processed the poly A tail will adhere to the oligo T and will not come out of the column without elution.
8. Which of the following codon calls for fMettRNA –fMet?
a) CTA
b) GUA
c) AUG
d) AUA
Explanation: AUG is the start codon for translation, and it incorporates formyl methinonyl tRNA to start translation. The 1st base is always an f-Met although it may be later cleaved off.
9. AUG is the universal start codon.
a) True
b) False
Explanation: While there is a common belief of AUG being the universal start codon, mitochondrial ribosomes doesn’t recognize it as so. Also GUG can act as a start codon in some cases undermining AUG.
10. What is meant by degenerate codon?
a) Two codons can be read in different frame o give different amino acids
b) Codons are not having a gap
c) Specific codon codes for specific amino acid
d) Two codons can code for same amino acid
Explanation: Degeneracy means that there can be two or more codons that can code for same amino acid with there being triplet codon and 4 bases there are 64 possible combinations and only 20 amino acids. This was then observed that different codon could be degenerate i.e. code for same amino acid.