Molecular Biology – Regulation of Gene Expression: NEET MCQs with Answers

15 free questions on Molecular Biology – Regulation of Gene Expression for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

Syllabus covered: Regulation of Gene Expression: Gene expression and regulation- Lac Operon;

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Question 1

Previous-year question
Match the genes of the lac operon with their respective products. (A) i gene, (B) z gene, (C) a gene, (D) y gene, with (i) β-galactosidase, (ii) permease, (iii) repressor, (iv) transacetylase. [NEET 2019]
  1. A–(i), B–(iii), C–(ii), D–(iv)
  2. A–(iii), B–(i), C–(ii), D–(iv)
  3. A–(iii), B–(i), C–(iv), D–(ii)
  4. A–(iii), B–(iv), C–(i), D–(ii)
Show answer
Answer: (C) A–(iii), B–(i), C–(iv), D–(ii)
Explanation: The i gene codes for the repressor, the z gene for β-galactosidase, the a gene for transacetylase and the y gene for permease.

Question 2

Previous-year question
Select the correct match. [NEET 2018]
  1. Alec Jeffreys – Streptococcus pneumoniae
  2. Alfred Hershey and Martha Chase – TMV
  3. Francois Jacob and Jacques Monod – Lac operon
  4. Matthew Meselson and F. Stahl – Pisum sativum
Show answer
Answer: (C) Francois Jacob and Jacques Monod – Lac operon
Explanation: Jacob and Monod proposed the operon model of gene regulation using the lac operon of E. coli. Alec Jeffreys developed DNA fingerprinting, Hershey and Chase worked with bacteriophages, and Meselson and Stahl worked with E. coli.

Question 3

Previous-year question
All of the following are part of an operon except [NEET 2018]
  1. An operator
  2. Structural genes
  3. A promoter
  4. An enhancer
Show answer
Answer: (D) An enhancer
Explanation: An operon comprises a promoter, an operator and the structural genes, under the control of a regulatory gene. Enhancers are eukaryotic cis-acting elements and are not part of a prokaryotic operon.

Question 4

Previous-year question
Which of the following is required as an inducer for the expression of the lac operon? [NEET 2016]
  1. Glucose
  2. Galactose
  3. Lactose
  4. Both lactose and galactose
Show answer
Answer: (C) Lactose
Explanation: Lactose is the substrate of β-galactosidase and acts as the inducer of the operon. It enters the cell through permease, is converted into allolactose and inactivates the repressor protein.

Question 5

Previous-year question
Gene regulation governing the lactose operon of E. coli that involves the lac I gene product is [AIPMT 2015]
  1. Negative and inducible because the repressor protein prevents transcription
  2. Negative and repressible because the repressor protein prevents transcription
  3. Feedback inhibition because excess β-galactosidase can switch off the operon
  4. Positive and inducible because it can be induced by lactose
Show answer
Answer: (A) Negative and inducible because the repressor protein prevents transcription
Explanation: The i (lac I) gene codes for a repressor that binds the operator and switches the operon off, which makes the control negative. Because the substrate lactose removes this repression, the operon is inducible.

Question 6

Previous-year question
The basis for DNA fingerprinting is [AIPMT 1996]
  1. occurrence of Restriction Fragment Length Polymorphism (RFLP)
  2. phenotypic differences between individuals
  3. availability of cloned DNA
  4. knowledge of human karyotype
Show answer
Answer: (A) occurrence of Restriction Fragment Length Polymorphism (RFLP)
Explanation: Restriction Fragment Length Polymorphism refers to differences among people in their DNA sequences at sites recognised by restriction enzymes. Such variation results in restriction fragments of different sizes, and RFLPs are used as markers in genomic mapping and DNA fingerprinting.

Question 7

Previous-year question
DNA fingerprinting refers to [AIPMT 2004]
  1. molecular analysis or profiles of DNA samples
  2. analysis of DNA samples using imprinting device
  3. techniques used for molecular analysis of different specimens of DNA
  4. techniques used for identification of finger-prints of individuals
Show answer
Answer: (A) molecular analysis or profiles of DNA samples
Explanation: DNA fingerprinting refers to the molecular analysis or profiling of DNA samples. The technique was discovered by Alec Jeffreys in 1984 and is based on differences in repetitive DNA sequences between individuals.
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Question 8

Previous-year question
Satellite DNA is useful tool in [AIPMT 2010]
  1. organ transplantation
  2. sex-determination
  3. forensic science
  4. genetic engineering
Show answer
Answer: (C) forensic science
Explanation: Satellite DNA is a useful tool in forensic science. The polymorphism of minisatellite and microsatellite repeats is analysed for DNA fingerprinting or DNA profiling, which helps in the resolution of crimes and legal disputes.

Question 9

Previous-year question
Which of the following forms the basis of DNA Fingerprinting? [AIPMT 2012]
  1. The relative proportions of purines and pyrimidines in DNA
  2. Satellite DNA occurring as highly repeated short DNA segments
  3. The relative difference in the DNA occurrence in blood, skin and saliva
  4. The relative amount of DNA in the ridges and grooves of the fingerprints
Show answer
Answer: (B) Satellite DNA occurring as highly repeated short DNA segments
Explanation: Satellite DNA occurring as highly repeated short DNA segments (tandem repeats) forms the basis of DNA fingerprinting. These non-coding regions show a high degree of variability from person to person and can be used to establish identity or family relationships.

Question 10

Previous-year question
One of the most frequently used techniques in DNA fingerprinting is [NEET 2013]
  1. AFLP
  2. VNTR
  3. SSCP
  4. SCAR
Show answer
Answer: (B) VNTR
Explanation: VNTR (Variable Number of Tandem Repeats) is one of the most frequently used techniques in DNA fingerprinting. These short nucleotide repeats vary in copy number from person to person and belong to the class of satellite DNA called minisatellites.

Question 11

Previous-year question
Commonly used vectors for human genome sequencing are [AIPMT 2014]
  1. T-DNA
  2. BAC and YAC
  3. Expression Vectors
  4. T/A Cloning Vectors
Show answer
Answer: (B) BAC and YAC
Explanation: BAC (Bacterial Artificial Chromosome) and YAC (Yeast Artificial Chromosome) are the commonly used vectors for human genome sequencing, because they can carry very large DNA inserts required for sequencing whole chromosomal DNA.

Question 12

Previous-year question
Satellite DNA is important because it [AIPMT 2015]
  1. codes for proteins needed in cell cycle
  2. shows high degree of polymorphism in population and also the same degree of polymorphism in an individual, which is heritable from parents to children
  3. does not code for proteins and is same in all members of the population
  4. codes for enzymes needed for DNA replication
Show answer
Answer: (B) shows high degree of polymorphism in population and also the same degree of polymorphism in an individual, which is heritable from parents to children
Explanation: Satellite DNA forms the minor peaks after density gradient centrifugation of DNA. These repetitive sequences do not code for any protein but show a high degree of polymorphism that is heritable from parents to children, and hence they form the basis of DNA fingerprinting.

Question 13

Previous-year question
Which of the following is not required for any of the techniques of DNA fingerprinting available at present? [NEET 2016, Phase I]
  1. Zinc finger analysis
  2. Restriction enzymes
  3. DNA-DNA hybridisation
  4. Polymerase chain reaction
Show answer
Answer: (A) Zinc finger analysis
Explanation: Zinc finger analysis is a technique for studying proteins containing zinc finger motifs that bind DNA, RNA or other ligands, and it has no role in DNA fingerprinting. Southern blotting, PCR, RFLP and DNA–DNA hybridisation are all used.

Question 14

Previous-year question
Expressed Sequence Tags (ESTs) refers to [NEET (National) 2019]
  1. polypeptide expression
  2. DNA polymorphism
  3. novel DNA sequences
  4. genes expressed as RNA
Show answer
Answer: (D) genes expressed as RNA
Explanation: Expressed Sequence Tags refer to the genes that are expressed as RNA. They are the DNA sequences that are transcribed as mRNA for protein synthesis, and identifying them is the shortcut approach to genome analysis.

Question 15

Previous-year question
Which is the basis of genetic mapping of human genome as well as DNA fingerprinting? [NEET (Oct.) 2020]
  1. Polymorphism in DNA sequence
  2. Single nucleotide polymorphism
  3. Polymorphism in mRNA sequence
  4. Polymorphism in RNA sequence
Show answer
Answer: (A) Polymorphism in DNA sequence
Explanation: Polymorphism in DNA sequence is the basis of genetic mapping of the human genome as well as of DNA fingerprinting. Polymorphism simply means variation at the genetic level, which arises due to mutations.

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