1. The term “Central Dogma” of molecular biology refers to:
A) DNA → RNA → Protein
B) Protein → RNA → DNA
C) RNA → DNA → Protein
D) Protein → DNA → RNA
Answer: A
Rationale: Crick’s central dogma describes the flow of genetic information from DNA to RNA to Protein.
2. Which enzyme is responsible for unwinding DNA during replication?
A) DNA polymerase
B) DNA ligase
C) DNA helicase
D) Primase
Answer: C
Rationale: DNA helicase breaks hydrogen bonds between strands, allowing replication fork formation.
3. Okazaki fragments are formed during:
A) Leading strand synthesis
B) Lagging strand synthesis
C) RNA transcription
D) Protein translation
Answer: B
Rationale: The lagging strand is synthesized discontinuously as Okazaki fragments.
4. Which of the following is a stop codon?
A) AUG
B) UAA
C) UGG
D) UAC
Answer: B
Rationale: UAA, UAG, and UGA are stop codons; AUG is the start codon.
5. The enzyme reverse transcriptase is mainly found in:
A) Bacteria
B) Retroviruses
C) Plants
D) Mitochondria
Answer: B
Rationale: Retroviruses use reverse transcriptase to synthesize DNA from RNA.
6. The genetic code is described as “degenerate” because:
A) Multiple codons can code for the same amino acid
B) Codons overlap
C) Codons are the same in all organisms
D) Codons never mutate
Answer: A
Rationale: More than one codon can specify the same amino acid (e.g., Leucine has 6 codons).
7. Which of the following mutations does NOT change the amino acid sequence?
A) Missense mutation
B) Nonsense mutation
C) Silent mutation
D) Frameshift mutation
Answer: C
Rationale: Silent mutations occur due to codon redundancy, not altering the protein.
8. Which technique is commonly used for amplifying DNA in vitro?
A) Gel electrophoresis
B) Northern blotting
C) PCR
D) Western blotting
Answer: C
Rationale: Polymerase Chain Reaction (PCR) amplifies DNA exponentially.
9. In eukaryotes, mRNA processing involves all EXCEPT:
A) 5′ capping
B) Polyadenylation
C) Splicing
D) Removing promoter sequence
Answer: D
Rationale: Promoter is upstream of the gene, not part of the transcript to be removed.
10. The operon model in prokaryotes was first proposed by:
A) Jacob and Monod
B) Watson and Crick
C) Hershey and Chase
D) Beadle and Tatum
Answer: A
Rationale: Jacob and Monod proposed the operon concept while studying lactose metabolism in E. coli.
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