51. The enzyme responsible for adding nucleotides in 5’ → 3’ direction during replication is:
A) DNA polymerase I
B) DNA polymerase III ✅
C) Ligase
D) Primase
Which DNA repair mechanism corrects mismatched bases immediately after replication?
A) Base excision repair
B) Nucleotide excision repair
C) Mismatch repair ✅
D) Homologous recombination
The term “degenerate code” in genetics means:
A) Multiple codons code for the same amino acid ✅
B) Each codon codes for multiple amino acids
C) Only one codon per amino acid
D) Codons are random
Which RNA molecule functions in the formation of spliceosomes?
A) tRNA
B) rRNA
C) snRNA ✅
D) miRNA
A nucleotide consists of:
A) Sugar + phosphate + amino acid
B) Sugar + base + phosphate ✅
C) Base + phosphate only
D) Sugar + base only
In prokaryotic replication, DNA polymerase III synthesizes:
A) Leading strand ✅
B) Lagging strand
C) RNA primers
D) Okazaki fragments
Which of the following sequences is palindromic in DNA?
A) 5’–GAATTC–3’ ✅
B) 5’–AGCT–3’
C) 5’–AAGG–3’
D) 5’–GACT–3’
RNA differs from DNA by:
A) Presence of uracil ✅
B) Presence of thymine
C) Double-stranded structure
D) Lack of phosphate
The enzyme that synthesizes the RNA primer is:
A) DNA polymerase
B) Ligase
C) Primase ✅
D) Helicase
DNA replication is called semi-conservative because:
A) Entire molecule is new
B) Each new molecule contains one old strand ✅
C) Strands are dispersed
D) Only one strand is copied
Which process converts DNA into RNA?
A) Translation
B) Replication
C) Transcription ✅
D) Splicing
In eukaryotic mRNA, the 5’ cap is:
A) Poly-A tail
B) 7-methylguanosine ✅
C) Start codon
D) Terminator
The 3’ → 5’ exonuclease activity of DNA polymerase ensures:
A) Ligase function
B) Proofreading ✅
C) Priming
D) Helicase activity
Which DNA form is favored under dehydrating conditions?
A) A-DNA ✅
B) B-DNA
C) Z-DNA
D) C-DNA
During translation, the ribosome moves along mRNA in which direction?
A) 3’ → 5’
B) 5’ → 3’ ✅
C) Random
D) Both
Which type of RNA is the most abundant in the cell?
A) mRNA
B) rRNA ✅
C) tRNA
D) miRNA
The attachment site for amino acids in tRNA is:
A) Anticodon loop
B) 3’ CCA end ✅
C) D-loop
D) TΨC loop
DNA supercoiling is relieved by:
A) Helicase
B) Topoisomerase ✅
C) Ligase
D) Polymerase
The TATA box is associated with:
A) RNA splicing
B) Transcription initiation ✅
C) Translation initiation
D) DNA replication
Which molecule carries genetic information in retroviruses?
A) dsDNA
B) ssRNA ✅
C) tRNA
D) rRNA
The codon UAA is a:
A) Start codon
B) Stop codon ✅
C) Amino acid codon
D) Anticodon
Which is the antiparallel strand to 5’–ATCG–3’?
A) 5’–TAGC–3’
B) 3’–TAGC–5’ ✅
C) 3’–ATCG–5’
D) 5’–ATCG–3’
DNA methylation primarily occurs at:
A) Adenine
B) Guanine
C) Cytosine ✅
D) Thymine
Ribozymes are:
A) DNA molecules
B) Protein enzymes
C) RNA molecules with catalytic activity ✅
D) Lipid molecules
Which nucleotide triphosphate is used in DNA synthesis?
A) NDP
B) NTP ✅
C) AMP
D) ADP
The poly-A tail in mRNA is located at:
A) 5’ end
B) 3’ end ✅
C) Middle
D) Both ends
Okazaki fragments are joined by:
A) DNA polymerase III
B) DNA polymerase I
C) Ligase ✅
D) Primase
The term “anticodon” refers to:
A) DNA segment
B) mRNA codon
C) tRNA triplet complementary to codon ✅
D) Ribosome site
Which of the following is a tertiary structure feature of tRNA?
A) Cloverleaf
B) L-shaped ✅
C) Double helix
D) Triplex
RNA interference (RNAi) involves which molecule?
A) rRNA
B) tRNA
C) siRNA ✅
D) mRNA
During replication, leading strand synthesis is:
A) Continuous ✅
B) Discontinuous
C) Random
D) Lagging
Which nitrogenous base pairs with guanine?
A) Thymine
B) Cytosine ✅
C) Adenine
D) Uracil
In eukaryotic cells, translation occurs in:
A) Nucleus
B) Cytoplasm ✅
C) Mitochondria
D) Endoplasmic reticulum
The process of converting RNA to protein is called:
A) Transcription
B) Translation ✅
C) Replication
D) Splicing
In the lac operon, the operator functions as:
A) RNA polymerase binding site
B) Repressor binding site ✅
C) Start codon
D) Promoter
Which of the following is a histone modification affecting gene expression?
A) Phosphorylation ✅
B) Glycosylation
C) Methylation
D) Ubiquitination
The origin recognition complex (ORC) is required for:
A) DNA replication initiation ✅
B) Transcription initiation
C) Translation
D) RNA processing
The enzyme telomerase synthesizes:
A) DNA at replication fork
B) RNA primers
C) Telomeric DNA repeats ✅
D) mRNA cap
The codon GGG codes for which amino acid?
A) Glycine ✅
B) Glutamine
C) Alanine
D) Arginine
The anticodon loop of tRNA binds to:
A) DNA template
B) Ribosome
C) mRNA codon ✅
D) Amino acid
Which is true about Z-DNA?
A) Right-handed helix
B) Left-handed helix ✅
C) B-form under physiological conditions
D) RNA double helix
DNA polymerase requires which cofactor?
A) Mg²⁺ ✅
B) Zn²⁺
C) K⁺
D) Na⁺
The term “exon” refers to:
A) Non-coding region
B) Coding region ✅
C) RNA primer
D) Anticodon
Which RNA is involved in RNA editing?
A) mRNA
B) gRNA ✅
C) tRNA
D) rRNA
Transcription factors bind to:
A) Promoter regions ✅
B) Ribosome
C) tRNA
D) Okazaki fragments
Which type of bond stabilizes the DNA double helix?
A) Covalent
B) Hydrogen ✅
C) Ionic
D) Peptide
The eukaryotic ribosome is:
A) 50S
B) 70S
C) 80S ✅
D) 60S
The enzyme that removes supercoils ahead of the replication fork is:
A) Ligase
B) Helicase
C) Topoisomerase ✅
D) Polymerase
Which codon is the universal start codon?
A) UAA
B) AUG ✅
C) UAG
D) UGA
100.During DNA replication, the parental DNA strand serves as:
A) Template ✅
B) Primer
C) Leading strand
D) Okazaki fragment