1. Which of the following is a purine base in nucleic acids?
A) Cytosine
B) Thymine
C) Adenine ✅
D) Uracil
Which bond links the sugar and phosphate backbone in nucleic acids?
A) Hydrogen bond
B) Phosphodiester bond ✅
C) Glycosidic bond
D) Peptide bond
In RNA, thymine is replaced by:
A) Cytosine
B) Uracil ✅
C) Adenine
D) Guanine
The backbone of DNA is formed by:
A) Hydrogen bonds
B) Phosphate and sugar ✅
C) Nitrogenous bases
D) Amino acids
Which enzyme synthesizes RNA from a DNA template?
A) DNA polymerase
B) RNA polymerase ✅
C) Ligase
D) Helicase
Chargaff’s rule states that:
A) A = T and C = G ✅
B) A = C and G = T
C) A + T = C + G
D) A = G and T = C
The direction of DNA replication is:
A) 3’ → 5’
B) 5’ → 3’ ✅
C) Bidirectional
D) Random
Which RNA carries amino acids to the ribosome?
A) mRNA
B) tRNA ✅
C) rRNA
D) snRNA
Which type of RNA is a structural component of ribosomes?
A) mRNA
B) tRNA
C) rRNA ✅
D) miRNA
Which of the following enzymes removes RNA primers during DNA replication?
A) DNA polymerase I ✅
B) DNA polymerase III
C) Ligase
D) Helicase
DNA replication in eukaryotes is:
A) Conservative
B) Semi-conservative ✅
C) Dispersive
D) Random
The primary structure of nucleic acids refers to:
A) Sequence of nucleotides ✅
B) Double helix
C) Supercoiling
D) Hydrogen bonding
Which base pairing is present in DNA?
A) A–U, G–C
B) A–T, G–C ✅
C) A–G, T–C
D) A–C, G–T
During transcription, the template strand is read in which direction?
A) 5’ → 3’
B) 3’ → 5’ ✅
C) Random
D) Both directions
Which nucleotide is present in both DNA and RNA?
A) Thymine
B) Uracil
C) Adenine ✅
D) None
Which DNA form is most common in cells under physiological conditions?
A) A-DNA
B) B-DNA ✅
C) Z-DNA
D) C-DNA
Telomeres are rich in which base?
A) Adenine
B) Guanine ✅
C) Cytosine
D) Thymine
Okazaki fragments are synthesized on:
A) Leading strand
B) Lagging strand ✅
C) Both strands
D) RNA primer
Which enzyme relieves supercoiling during DNA replication?
A) Helicase
B) Topoisomerase ✅
C) Ligase
D) Polymerase
In prokaryotes, DNA replication begins at:
A) Telomere
B) Origin of replication ✅
C) Centromere
D) Enhancer
In transcription, which sequence signals termination?
A) Promoter
B) Terminator ✅
C) Operator
D) Enhancer
RNA splicing occurs in:
A) Prokaryotes
B) Eukaryotes ✅
C) Both
D) None
Which of the following is not a nucleic acid?
A) DNA
B) RNA
C) ATP
D) Polysaccharide ✅
Which type of RNA regulates gene expression post-transcriptionally?
A) mRNA
B) tRNA
C) miRNA ✅
D) rRNA
The ribose sugar in RNA has which group at 2’ carbon?
A) H
B) OH ✅
C) O
D) CH3
The first step of DNA replication is:
A) Ligase activity
B) Helicase unwinding ✅
C) Primer synthesis
D) Okazaki fragment joining
The enzyme that joins Okazaki fragments is:
A) DNA polymerase I
B) DNA polymerase III
C) Ligase ✅
D) Helicase
The central dogma of molecular biology states:
A) Protein → DNA → RNA
B) DNA → RNA → Protein ✅
C) RNA → DNA → Protein
D) DNA → Protein → RNA
Which DNA repair mechanism removes thymine dimers?
A) Base excision repair
B) Nucleotide excision repair ✅
C) Mismatch repair
D) Homologous recombination
In the genetic code, how many nucleotides code for one amino acid?
A) 1
B) 2
C) 3 ✅
D) 4
In a tRNA molecule, the anticodon binds to:
A) DNA
B) mRNA codon ✅
C) Ribosome
D) Amino acid
During transcription, RNA is synthesized from:
A) Ribose sugar
B) Nucleotide triphosphates ✅
C) Amino acids
D) DNA backbone
Which of the following sequences is complementary to 5’–AGCT–3’?
A) 5’–TCGA–3’ ✅
B) 5’–AGCT–3’
C) 3’–AGCT–5’
D) 3’–TCGA–5’
The Shine–Dalgarno sequence is found in:
A) Eukaryotic mRNA
B) Prokaryotic mRNA ✅
C) tRNA
D) rRNA
Which nucleic acid carries the genetic information in viruses like HIV?
A) DNA
B) dsRNA
C) ssRNA ✅
D) Protein
Which form of DNA has left-handed helix?
A) A-DNA
B) B-DNA
C) Z-DNA ✅
D) C-DNA
Which molecule is used as an energy source in polymerization of nucleic acids?
A) ADP
B) NTP ✅
C) AMP
D) NAD
The major groove of DNA is important for:
A) Base pairing
B) Protein binding ✅
C) Sugar linkage
D) Phosphate linkage
Which process converts pre-mRNA to mature mRNA?
A) Transcription
B) Translation
C) RNA processing ✅
D) Replication
Which amino acid is specified by the start codon AUG?
A) Glycine
B) Methionine ✅
C) Alanine
D) Phenylalanine
DNA polymerase III is primarily responsible for:
A) Leading strand synthesis ✅
B) Lagging strand ligation
C) RNA primer removal
D) DNA repair
In histone-DNA complexes, DNA wraps around:
A) 4 histones
B) 8 histones ✅
C) 2 histones
D) 10 histones
Which of the following is a single-stranded nucleic acid in cells?
A) DNA
B) mRNA ✅
C) tRNA
D) rRNA
Which type of RNA is involved in RNA splicing?
A) mRNA
B) snRNA ✅
C) tRNA
D) rRNA
In eukaryotic cells, transcription occurs in:
A) Cytoplasm
B) Nucleus ✅
C) Ribosome
D) Mitochondria
DNA ligase forms which type of bond?
A) Hydrogen bond
B) Phosphodiester bond ✅
C) Peptide bond
D) Glycosidic bond
Which molecule acts as a primer during DNA replication?
A) DNA polymerase
B) RNA ✅
C) Protein
D) Ligase
The enzyme that unwinds DNA during replication is:
A) Topoisomerase
B) Helicase ✅
C) Ligase
D) Polymerase
The wobble hypothesis is related to:
A) DNA replication
B) RNA transcription
C) tRNA codon-anticodon pairing ✅
D) Ribosome assembly
50. The end of linear eukaryotic chromosomes is protected by:
A) Centromere
B) Telomere ✅
C) Operator
D) Promoter