This set of Molecular Biology Multiple Choice Questions & Answers (MCQs) focuses on “The Concept of the Replicon”.
1. Who of the following was not one of the scientists explaining the replicon model?
a) Francois Jacob
b) Sydney Brenner
c) Jacques Cuzin
d) Arthur Kornberg
View Answer
Explanation: Arthur Kornberg was the first to isolate DNA polymerase from E. coli. Francois Jacob, Sydney Brenner and Jacques Cuzin proposed a model explaining the events controlling the initiation of replication in bacteria known as the replicon model in 1963.
2. The replicon model was first explained in the year ____________
a) 1950
b) 1957
c) 1963
d) 1968
View Answer
Explanation: In 1963 Francois Jacob, Sydney Brenner and Jacques Cuzin proposed a model explaining the events controlling the initiation of replication in bacteria. They defined that the entire DNA of bacteria is replicated from a particular origin and thus termed the model a replicon.
3. The eukaryotic chromosome has a single replicon.
a) True
b) False
View Answer
Explanation: A replicon is a stretch of DNA that is replicated from a single origin. The E. coli is so small that it has only one origin of replication thus have only one replicon. The eukaryotic chromosome is large and the replication of the whole genome is complicated thus it has multiple origin of replications giving rise to multiple replicons.
4. The replicon model comprises of an initiator and _______________
a) Replicator
b) Origin of replication
c) Dna A protein
d) AT rich DNA
View Answer
Explanation: The replicon model comprises of an initiator and a replicator. The initiator protein helps in the recognition of the DNA element in the replicator and activates the process of initiation. The replicator is the cis – acting DNA segment that directs the initiation of DNA replication.
5. Replicator is the synonym for origin of replication.
a) True
b) False
View Answer
Explanation: The replicator is the cis – acting DNA segment that directs the initiation of DNA replication. But the origin of replication is the site on the DNA where the DNA is unwound and the replication initiates.
6. The initiator protein binds to a segment ____________ of the replicator sequence.
a) Upstream
b) Downstream
c) At the end
d) Within
View Answer
Explanation: The initiator protein binds to a segment within the replicator sequence. This protein finally attaching to its specific sequence activates the initiation of replication by recruiting different replication enzymes and signaling the unwinding of DNA.
7. Binding of the Dna A protein to the DNA is energy dependent.
a) True
b) False
View Answer
Explanation: The Dna A protein binds to the repeated 9 mer region of the ori C and is regulated by ATP. When bound to ATP, Dna A interacts with DNA in the region of the repeated 13 mer repeats of ori C.
8. Assembly of how many proteins make up the origin replication complex (ORC) in eukaryotes?
a) 2
b) 4
c) 6
d) 8
View Answer
Explanation: In eukaryotes the initiator is a 6 protein complex called the origin replication complex (ORC). The function of ORC is best understood in yeast cells.
9. Which of the following proteins is not recruited by Dna A protein?
a) Dna A protein
b) Helicase
c) Dna C protein
d) SSB protein
View Answer
Explanation: Dna A recruits a complex of two proteins, the helicase, Dna B protein and the helicase loader (Dna C). Both proteins are present in 6 copies within the complex. The DNA helicase is maintained in an inactive state in the helicase – helicase loader complex.
Sanfoundry Global Education & Learning Series – Molecular Biology.
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