Complete Molecular Basis of Inheritance Question Bank & Solutions (71 Questions)
Q1 of 71
NEET NCERT Line-by-Line
DNA is a polymer of:
(A)
Amino acids
(B)
Deoxyribonucleotides
(C)
Ribonucleotides
(D)
Fatty acids
Show Answer & NCERT Explanation
Correct Answer: (B) Deoxyribonucleotides
DNA is a polymer of deoxyribonucleotides.
Q2 of 71
NEET NCERT Line-by-Line
The genome size of E. coli is:
(A)
5386 bp
(B)
48,502 bp
(C)
4.6 × 10⁶ bp
(D)
3.3 × 10⁹ bp
Show Answer & NCERT Explanation
Correct Answer: (C) 4.6 × 10⁶ bp
E. coli ≈ 4.6 million bp.
Q3 of 71
NEET NCERT Line-by-Line
Which of these is a purine?
(A)
Cytosine
(B)
Thymine
(C)
Uracil
(D)
Guanine
Show Answer & NCERT Explanation
Correct Answer: (D) Guanine
Adenine and Guanine are purines.
Q4 of 71
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In RNA, thymine is replaced by:
(A)
Cytosine
(B)
Uracil
(C)
Guanine
(D)
Adenine
Show Answer & NCERT Explanation
Correct Answer: (B) Uracil
Uracil replaces thymine in RNA.
Q5 of 71
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A nucleoside consists of:
(A)
Base + phosphate
(B)
Base + sugar
(C)
Sugar + phosphate
(D)
Base + sugar + phosphate
Show Answer & NCERT Explanation
Correct Answer: (B) Base + sugar
Nucleoside = base + sugar; adding phosphate gives a nucleotide.
Q6 of 71
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Nucleotides are linked by:
(A)
Peptide bonds
(B)
Hydrogen bonds
(C)
Phosphodiester bonds
(D)
Glycosidic bonds
Show Answer & NCERT Explanation
Correct Answer: (C) Phosphodiester bonds
3′–5′ phosphodiester bonds form the backbone.
Q7 of 71
NEET NCERT Line-by-Line
The DNA double helix was proposed in:
(A)
1928
(B)
1944
(C)
1953
(D)
1961
Show Answer & NCERT Explanation
Correct Answer: (C) 1953
Watson and Crick, 1953.
Q8 of 71
NEET NCERT Line-by-Line
Chargaff's rule states that:
(A)
A = G
(B)
A = T and G = C
(C)
A + G = C
(D)
Purines = 2 × pyrimidines
Show Answer & NCERT Explanation
Correct Answer: (B) A = T and G = C
A pairs T, G pairs C; purines = pyrimidines.
Q9 of 71
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The two strands of DNA are:
(A)
Parallel
(B)
Antiparallel
(C)
Identical
(D)
Both 5′→3′
Show Answer & NCERT Explanation
Correct Answer: (B) Antiparallel
They run antiparallel (5′→3′ and 3′→5′).
Q10 of 71
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How many hydrogen bonds are between G and C?
Show Answer & NCERT Explanation
Correct Answer: (C) 3
G≡C has three hydrogen bonds.
Q11 of 71
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The distance between two adjacent base pairs is:
(A)
0.34 nm
(B)
3.4 nm
(C)
2 nm
(D)
10 nm
Show Answer & NCERT Explanation
Correct Answer: (A) 0.34 nm
0.34 nm; a full turn (pitch) is 3.4 nm.
Q12 of 71
NEET NCERT Line-by-Line
Number of base pairs per turn of B-DNA is about:
(A)
5
(B)
10
(C)
15
(D)
20
Show Answer & NCERT Explanation
Correct Answer: (B) 10
About 10 bp per 3.4 nm turn.
Q13 of 71
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The diameter of the DNA helix is:
(A)
1 nm
(B)
2 nm
(C)
3.4 nm
(D)
0.34 nm
Show Answer & NCERT Explanation
Correct Answer: (B) 2 nm
A uniform 2 nm.
Q14 of 71
NEET NCERT Line-by-Line
The Central Dogma was proposed by:
(A)
Watson
(B)
Crick
(C)
Nirenberg
(D)
Khorana
Show Answer & NCERT Explanation
Correct Answer: (B) Crick
Francis Crick proposed the central dogma.
Q15 of 71
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Reverse transcription (RNA → DNA) occurs in:
(A)
Bacteria
(B)
Retroviruses
(C)
Fungi
(D)
All eukaryotes
Show Answer & NCERT Explanation
Correct Answer: (B) Retroviruses
Retroviruses use reverse transcriptase.
Q16 of 71
NEET NCERT Line-by-Line
Histones are rich in the amino acids:
(A)
Glutamate & aspartate
(B)
Lysine & arginine
(C)
Glycine & alanine
(D)
Cysteine & methionine
Show Answer & NCERT Explanation
Correct Answer: (B) Lysine & arginine
Lysine and arginine give histones a positive charge.
Q17 of 71
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A nucleosome contains DNA of about:
(A)
50 bp
(B)
100 bp
(C)
200 bp
(D)
500 bp
Show Answer & NCERT Explanation
Correct Answer: (C) 200 bp
~200 bp wound on a histone octamer.
Q18 of 71
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Transcriptionally active chromatin is:
(A)
Heterochromatin
(B)
Euchromatin
(C)
Satellite DNA
(D)
Telomere
Show Answer & NCERT Explanation
Correct Answer: (B) Euchromatin
Euchromatin is loosely packed and active.
Q19 of 71
NEET NCERT Line-by-Line
Griffith worked with the bacterium:
(A)
E. coli
(B)
Streptococcus pneumoniae
(C)
Salmonella
(D)
Bacillus
Show Answer & NCERT Explanation
Correct Answer: (B) Streptococcus pneumoniae
He used Streptococcus pneumoniae (Diplococcus).
Q20 of 71
NEET NCERT Line-by-Line
The transforming principle was identified as DNA by:
(A)
Griffith
(B)
Hershey & Chase
(C)
Avery, MacLeod & McCarty
(D)
Meselson & Stahl
Show Answer & NCERT Explanation
Correct Answer: (C) Avery, MacLeod & McCarty
Their enzyme experiments showed DNA is the transforming principle.
Q21 of 71
NEET NCERT Line-by-Line
Hershey and Chase used which radioactive isotopes?
(A)
¹⁴C and ³H
(B)
³²P and ³⁵S
(C)
¹⁵N and ¹⁴N
(D)
¹²⁵I and ³²P
Show Answer & NCERT Explanation
Correct Answer: (B) ³²P and ³⁵S
³²P labelled DNA, ³⁵S labelled protein.
Q22 of 71
NEET NCERT Line-by-Line
In Hershey–Chase, which entered the bacteria?
(A)
³⁵S protein
(B)
³²P DNA
(C)
Both
(D)
Neither
Show Answer & NCERT Explanation
Correct Answer: (B) ³²P DNA
³²P (DNA) entered — proving DNA is genetic material.
Q23 of 71
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RNA is less stable than DNA mainly because of:
(A)
Thymine
(B)
The 2′-OH group
(C)
Phosphate
(D)
Double strands
Show Answer & NCERT Explanation
Correct Answer: (B) The 2′-OH group
The reactive 2′-OH makes RNA labile.
Q24 of 71
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The likely first genetic material was:
(A)
DNA
(B)
Protein
(C)
RNA
(D)
Lipid
Show Answer & NCERT Explanation
Correct Answer: (C) RNA
The RNA world hypothesis: RNA came first.
Q25 of 71
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DNA replication is:
(A)
Conservative
(B)
Semiconservative
(C)
Dispersive
(D)
Random
Show Answer & NCERT Explanation
Correct Answer: (B) Semiconservative
Each daughter has one old and one new strand.
Q26 of 71
NEET NCERT Line-by-Line
Semiconservative replication was proved by:
(A)
Watson & Crick
(B)
Meselson & Stahl
(C)
Griffith
(D)
Jacob & Monod
Show Answer & NCERT Explanation
Correct Answer: (B) Meselson & Stahl
Meselson and Stahl (1958).
Q27 of 71
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Meselson and Stahl used:
(A)
Radioactive P
(B)
Heavy nitrogen ¹⁵N
(C)
³⁵S
(D)
Fluorescent dye
Show Answer & NCERT Explanation
Correct Answer: (B) Heavy nitrogen ¹⁵N
¹⁵N (heavy) and CsCl density-gradient centrifugation.
Q28 of 71
NEET NCERT Line-by-Line
DNA polymerase synthesises DNA in the direction:
(A)
3′→5′
(B)
5′→3′
(C)
Both
(D)
Random
Show Answer & NCERT Explanation
Correct Answer: (B) 5′→3′
Always 5′→3′.
Q29 of 71
NEET NCERT Line-by-Line
The discontinuously synthesised strand produces:
(A)
Primers
(B)
Okazaki fragments
(C)
Introns
(D)
Codons
Show Answer & NCERT Explanation
Correct Answer: (B) Okazaki fragments
Okazaki fragments on the lagging strand.
Q30 of 71
NEET NCERT Line-by-Line
Okazaki fragments are joined by:
(A)
Helicase
(B)
Primase
(C)
DNA ligase
(D)
Topoisomerase
Show Answer & NCERT Explanation
Correct Answer: (C) DNA ligase
DNA ligase seals the fragments.
Q31 of 71
NEET NCERT Line-by-Line
DNA replication occurs during which phase?
(A)
G1
(B)
S
(C)
G2
(D)
M
Show Answer & NCERT Explanation
Correct Answer: (B) S
The S-phase of interphase.
Q32 of 71
NEET NCERT Line-by-Line
The DNA strand that is copied is the:
(A)
Coding strand
(B)
Sense strand
(C)
Template strand
(D)
Both strands
Show Answer & NCERT Explanation
Correct Answer: (C) Template strand
Only the template (3′→5′) strand is transcribed.
Q33 of 71
NEET NCERT Line-by-Line
A transcription unit has, in order:
(A)
Terminator–gene–promoter
(B)
Promoter–structural gene–terminator
(C)
Operator–gene–promoter
(D)
Gene–promoter–terminator
Show Answer & NCERT Explanation
Correct Answer: (B) Promoter–structural gene–terminator
Promoter, structural gene, terminator.
Q34 of 71
NEET NCERT Line-by-Line
In bacteria, transcription is terminated with the help of:
(A)
Sigma factor
(B)
Rho factor
(C)
Ligase
(D)
Primase
Show Answer & NCERT Explanation
Correct Answer: (B) Rho factor
The ρ (rho) factor aids termination.
Q35 of 71
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In eukaryotes, mRNA precursor (hnRNA) is made by:
(A)
RNA Pol I
(B)
RNA Pol II
(C)
RNA Pol III
(D)
DNA Pol
Show Answer & NCERT Explanation
Correct Answer: (B) RNA Pol II
RNA polymerase II makes hnRNA.
Q36 of 71
NEET NCERT Line-by-Line
Introns are:
(A)
Coding sequences
(B)
Non-coding intervening sequences
(C)
Promoters
(D)
Poly-A tails
Show Answer & NCERT Explanation
Correct Answer: (B) Non-coding intervening sequences
Introns are removed during splicing; exons are expressed.
Q37 of 71
NEET NCERT Line-by-Line
Capping of hnRNA adds ___ at the 5′ end.
(A)
Poly-A
(B)
Methyl guanosine triphosphate
(C)
Uracil
(D)
Sigma factor
Show Answer & NCERT Explanation
Correct Answer: (B) Methyl guanosine triphosphate
A methyl guanosine triphosphate cap.
Q38 of 71
NEET NCERT Line-by-Line
The triplet nature of the genetic code was proposed by:
(A)
Nirenberg
(B)
Khorana
(C)
George Gamow
(D)
Ochoa
Show Answer & NCERT Explanation
Correct Answer: (C) George Gamow
George Gamow proposed the triplet code.
Q39 of 71
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How many of the 64 codons are stop codons?
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Correct Answer: (C) 3
Three: UAA, UAG, UGA.
Q40 of 71
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The start codon is:
(A)
UAA
(B)
AUG
(C)
UGA
(D)
GUG
Show Answer & NCERT Explanation
Correct Answer: (B) AUG
AUG (also codes methionine).
Q41 of 71
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That most amino acids have more than one codon shows the code is:
(A)
Ambiguous
(B)
Overlapping
(C)
Degenerate
(D)
Non-universal
Show Answer & NCERT Explanation
Correct Answer: (C) Degenerate
This is degeneracy of the code.
Q42 of 71
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The adaptor molecule in translation is:
(A)
mRNA
(B)
rRNA
(C)
tRNA
(D)
hnRNA
Show Answer & NCERT Explanation
Correct Answer: (C) tRNA
tRNA, as postulated by Crick.
Q43 of 71
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The catalytic (ribozyme) role in the ribosome is played by:
(A)
Protein
(B)
rRNA
(C)
tRNA
(D)
mRNA
Show Answer & NCERT Explanation
Correct Answer: (B) rRNA
rRNA acts as the ribozyme.
Q44 of 71
NEET NCERT Line-by-Line
The lac operon was described by:
(A)
Watson & Crick
(B)
Jacob & Monod
(C)
Beadle & Tatum
(D)
Hershey & Chase
Show Answer & NCERT Explanation
Correct Answer: (B) Jacob & Monod
François Jacob and Jacques Monod.
Q45 of 71
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The inducer of the lac operon is:
(A)
Glucose
(B)
Lactose
(C)
Galactose
(D)
Repressor
Show Answer & NCERT Explanation
Correct Answer: (B) Lactose
Lactose inactivates the repressor.
Q46 of 71
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The z gene of the lac operon codes for:
(A)
Permease
(B)
Transacetylase
(C)
β-galactosidase
(D)
Repressor
Show Answer & NCERT Explanation
Correct Answer: (C) β-galactosidase
β-galactosidase splits lactose.
Q47 of 71
NEET NCERT Line-by-Line
The Human Genome Project ran from:
(A)
1985–1995
(B)
1990–2003
(C)
2000–2010
(D)
1975–1990
Show Answer & NCERT Explanation
Correct Answer: (B) 1990–2003
1990 to 2003.
Q48 of 71
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The largest human gene is:
(A)
Haemoglobin
(B)
Dystrophin
(C)
Insulin
(D)
Collagen
Show Answer & NCERT Explanation
Correct Answer: (B) Dystrophin
Dystrophin (~2.4 million bases).
Q49 of 71
NEET NCERT Line-by-Line
DNA fingerprinting was developed by:
(A)
Alec Jeffreys
(B)
Kary Mullis
(C)
Fred Sanger
(D)
Har Gobind Khorana
Show Answer & NCERT Explanation
Correct Answer: (A) Alec Jeffreys
Alec Jeffreys developed it, using VNTRs.
Q50 of 71
NEET NCERT Line-by-Line
DNA fingerprinting is based on polymorphism in:
(A)
Exons
(B)
Promoters
(C)
VNTR / satellite DNA
(D)
tRNA genes
Show Answer & NCERT Explanation
Correct Answer: (C) VNTR / satellite DNA
Variable Number of Tandem Repeats (satellite DNA).
Q51 of 71
NEET NCERT Line-by-Line
The sugar present in DNA is:
(A)
Ribose
(B)
Deoxyribose
(C)
Glucose
(D)
Fructose
Show Answer & NCERT Explanation
Correct Answer: (B) Deoxyribose
DNA has deoxyribose (lacks the 2′-OH of ribose).
Q52 of 71
NEET NCERT Line-by-Line
A newly synthesised DNA strand grows in the direction:
(A)
3′ → 5′
(B)
5′ → 3′
(C)
Both directions equally
(D)
Randomly
Show Answer & NCERT Explanation
Correct Answer: (B) 5′ → 3′
Polymerase adds nucleotides to the free 3′-OH end.
Q53 of 71
NEET NCERT Line-by-Line
The enzyme that unwinds the DNA double helix is:
(A)
Ligase
(B)
Helicase
(C)
Primase
(D)
Polymerase III
Show Answer & NCERT Explanation
Correct Answer: (B) Helicase
Helicase separates the two strands at the fork.
Q54 of 71
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Okazaki fragments are joined together by:
(A)
Helicase
(B)
Primase
(C)
DNA ligase
(D)
Topoisomerase
Show Answer & NCERT Explanation
Correct Answer: (C) DNA ligase
DNA ligase seals the nicks on the lagging strand.
Q55 of 71
NEET NCERT Line-by-Line
The wobble position of a codon is the:
(A)
First base
(B)
Second base
(C)
Third base
(D)
Anticodon loop
Show Answer & NCERT Explanation
Correct Answer: (C) Third base
Relaxed pairing at the third base underlies degeneracy.
Q56 of 71
NEET NCERT Line-by-Line
A tRNA is charged with its amino acid by:
(A)
Peptidyl transferase
(B)
Aminoacyl-tRNA synthetase
(C)
RNA polymerase
(D)
Reverse transcriptase
Show Answer & NCERT Explanation
Correct Answer: (B) Aminoacyl-tRNA synthetase
This enzyme uses ATP to attach the correct amino acid.
Q57 of 71
NEET NCERT Line-by-Line
The 5′ cap of eukaryotic mRNA is:
(A)
Poly-A
(B)
Methyl guanosine triphosphate
(C)
A stop codon
(D)
An intron
Show Answer & NCERT Explanation
Correct Answer: (B) Methyl guanosine triphosphate
Methyl-GTP cap aids ribosome binding and protection.
Q58 of 71
NEET NCERT Line-by-Line
In eukaryotes, tRNA is transcribed by:
(A)
RNA polymerase I
(B)
RNA polymerase II
(C)
RNA polymerase III
(D)
DNA polymerase
Show Answer & NCERT Explanation
Correct Answer: (C) RNA polymerase III
Pol III makes tRNA, 5S rRNA and snRNAs.
Q59 of 71
NEET NCERT Line-by-Line
The site on the ribosome that receives incoming aminoacyl-tRNA is the:
(A)
P-site
(B)
A-site
(C)
E-site
(D)
Operator
Show Answer & NCERT Explanation
Correct Answer: (B) A-site
The A-site accepts the new aminoacyl-tRNA.
Q60 of 71
NEET NCERT Line-by-Line
The initiator amino acid in translation is:
(A)
Valine
(B)
Methionine
(C)
Glycine
(D)
Leucine
Show Answer & NCERT Explanation
Correct Answer: (B) Methionine
AUG codes for methionine, the start amino acid.
Q61 of 71
NEET NCERT Line-by-Line
DNA fingerprinting relies on polymorphism in:
(A)
Exons
(B)
VNTRs (tandem repeats)
(C)
Ribosomal RNA
(D)
Introns of the lac operon
Show Answer & NCERT Explanation
Correct Answer: (B) VNTRs (tandem repeats)
Variable Number Tandem Repeats differ between individuals.
Q62 of 71
NEET NCERT Line-by-Line
Tiny forensic DNA samples are amplified for fingerprinting using:
(A)
Southern blotting
(B)
PCR
(C)
Centrifugation
(D)
Electrophoresis alone
Show Answer & NCERT Explanation
Correct Answer: (B) PCR
PCR multiplies minute samples into detectable amounts.
Q63 of 71
NEET NCERT Line-by-Line
The operator of the lac operon is the site where the ___ binds:
(A)
Inducer
(B)
Repressor
(C)
RNA polymerase permanently
(D)
Ribosome
Show Answer & NCERT Explanation
Correct Answer: (B) Repressor
The repressor binds the operator to block transcription.
Q64 of 71
NEET NCERT Line-by-Line
The y gene of the lac operon codes for:
(A)
β-galactosidase
(B)
Permease
(C)
Transacetylase
(D)
Repressor
Show Answer & NCERT Explanation
Correct Answer: (B) Permease
Permease controls lactose entry into the cell.
Q65 of 71
NEET NCERT Line-by-Line
Splicing refers to the removal of:
(A)
Exons
(B)
Introns
(C)
The poly-A tail
(D)
The 5′ cap
Show Answer & NCERT Explanation
Correct Answer: (B) Introns
Introns are excised and exons joined to make mature mRNA.
Q66 of 71
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The poly-A tail is added to the ___ end of mRNA.
(A)
5′
(B)
3′
(C)
Both ends
(D)
Neither end
Show Answer & NCERT Explanation
Correct Answer: (B) 3′
The poly-A tail stabilises the 3′ end.
Q67 of 71
NEET NCERT Line-by-Line
The number of many origins of replication is characteristic of:
(A)
Prokaryotes
(B)
Eukaryotes
(C)
Viruses only
(D)
Plasmids
Show Answer & NCERT Explanation
Correct Answer: (B) Eukaryotes
Eukaryotic chromosomes replicate from multiple origins.
Q68 of 71
NEET NCERT Line-by-Line
RNA polymerase reads the template strand in the direction:
(A)
5′ → 3′
(B)
3′ → 5′
(C)
Both
(D)
Neither
Show Answer & NCERT Explanation
Correct Answer: (B) 3′ → 5′
It reads template 3′→5′ while building RNA 5′→3′.
Q69 of 71
NEET NCERT Line-by-Line
The 'ELSI' programme of the HGP dealt with:
(A)
Enzyme labelling
(B)
Ethical, legal and social issues
(C)
Electrophoresis standards
(D)
Exon–intron sizing
Show Answer & NCERT Explanation
Correct Answer: (B) Ethical, legal and social issues
ELSI addressed the societal implications of genome data.
Q70 of 71
NEET NCERT Line-by-Line
The near-universality of the genetic code is evidence for:
(A)
Independent origins of life
(B)
A common evolutionary ancestry
(C)
Lamarckism
(D)
Reverse transcription
Show Answer & NCERT Explanation
Correct Answer: (B) A common evolutionary ancestry
Shared codon meaning across life implies common descent.
Q71 of 71
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Which enzyme lays down the RNA primer needed to start replication?
(A)
Ligase
(B)
Primase
(C)
Helicase
(D)
Gyrase
Show Answer & NCERT Explanation
Correct Answer: (B) Primase
Primase synthesises the short RNA primer for polymerase.