O RNA motety Mutant A 5-UAAACGAG-3 Mutant B 5-UAAAGCAG-3\' Mutant C 5\'-UAAACGAG
ID: 150256 • Letter: O
Question
O RNA motety Mutant A 5-UAAACGAG-3 Mutant B 5-UAAAGCAG-3' Mutant C 5'-UAAACGAG-3 GUUUCGUC GUUUGCUC Question 15. The genome of the bacteriophage Oß consists of about 4000 nucleotides of single-stranded RNA. Inside the E.colihost, replication of this genome requires RNA polymerase made up of phage and bacterial proteins. Inter- estingly, the oplicase binds to a region in the center of the RNA genome, yet must start copying the 3 end of the RNA template to produce a new strand of RNA in the 5' to 3' direction. Research- GUUUGCUC a RNA-dependent In vitro replication efficiency (relative to wild type) wild type: 100% Mutant A: 1.6% Mutant B: 0.6% ers hypothesized that the presence ofa predicted pseudoknot in Mutant C: 42% the QB genome allowed the replicase to gain access to the 3'end of the RNA. To test their hypothesis, they measured the replication A. Predict why the replication efficiency so low in Mutant A efficiency in vitro using wild-type replicase and different ver- sions of the QB RNA containing mutations in a region key to the B. Predict why the replication efficiency is restored to almost predicted pseudoknot formation. They specifically focused on an eight-nucleotide region from the center of the RNA that was complementary to the 3'-terminal hairpin. The wild-type and the mutant sequences and replication data are given below. half of wild-type levels in Mutant C? C. Do you think the results support or refute the hypothesis that presence of a pseudoknot affects replication? Wild type 5'-UAAAGCAG-3 Data adapted from Klovins and van Duin (1999. J. Mol. Biol. GUUUCGUC 294: 875-884.Explanation / Answer
A.
replication efficiency was low in mutant A as it was not completemntary to the other RNA.
Hence, replication could not occur as it is based on base-pairing rules.
ie, CG paired with CG only and not GC.
B.
Replication efficiency was very high in mutant C as it had a very good complementary base pairing, just as in the wild type.
ie, CG was paired with GC which is ideal.
C.
Yes, the results support the above hypothesis.
Presence of pseudoknot increases replication as it has same complementary pairing as required to start replicating from 3' end.
It results in replication being occuring from 3' end when the polymerase binds to the middle of the RNA.
Hence, presence of pseudoknot increases the rate of replication.
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