Molecular Biology MCQ (Multiple Choice Questions)

Here are 1000 MCQs on Molecular Biology (Chapterwise).

1. What is Molecular Biology?
a) Deals with the physical structures and processes of biological events
b) Deals with the chemical structures and processes of chemical events
c) Deals with the physical structures and processes of chemical events
d) Deals with the chemical structures and processes of biological events
View Answer

Answer: d
Explanation: Molecular biology is a branch of biology that studies the chemical structures and processes of biological events involving molecules, the basic units of life. The study of molecular biology is concerned with nucleic acids (such as DNA and RNA) and proteins—macromolecules.

2. Which of the following is DNA made up of?
a) Adenine – Guanine
b) Cytosine – Thymine
c) Both Adenine – Guanine & Cytosine – Thymine
d) None of the mentioned
View Answer

Answer: c
Explanation: DNA is a linear molecule made up of four different types of nucleotide bases: adenine (A), cytosine (C), guanine (G), and thymine (T) (T). The DNA sequence is the order in which these bases appear.

3. Who is known as the father of Molecular biology?
a) Linus Carl Pauling
b) James Watson
c) Francis H. Crick
d) Mahlon B. Hoagland
View Answer

Answer: a
Explanation: Pauling was called the “Father of Molecular Biology” by Francis Crick. His discovery of sickle cell anaemia as a “molecular illness” paved the path for molecular analysis of genetically acquired alterations.

4. Proteins are made up of which of the following?
a) Nucleic acids
b) Amino acids
c) Nuclease
d) None of the mentioned
View Answer

Answer: b
Explanation: Proteins are made up of hundreds or thousands of smaller units known as amino acids that are linked in lengthy chains. A protein is made up of 20 different types of amino acids that can be combined in various ways.

5. Which of the following is RNA made up of?
a) Adenine, Cytosine, Guanine, and Uracil
b) Adenine, Guanine, Cytosine, and Thymine
c) Adenine, Guanine, Uracil, and Thymine
d) Adenine, Uracil, Cytosine, and Thymine
View Answer

Answer: d
Explanation: Ribonucleic acid (RNA) is a linear molecule made up of four different ribonucleotide bases: adenine (A), cytosine (C), guanine (G), and uracil (U).
advertisement
advertisement

6. Which of the following is a type of RNA involved in protein synthesis?
a) snRNA
b) rRNA
c) yRNA
d) dsRNA
View Answer

Answer: b
Explanation: Protein synthesis requires three different forms of RNA. Messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA are the three types of RNA (rRNA).

7. How many unusual bases are observed in a tRNA molecule?
a) 1
b) 3
c) 5
d) 0
View Answer

Answer: c
Explanation: Five unusual bases, produced by enzymatic modification of the usual bases, may be observed in a tRNA molecule. These are pseudouridine, dihyrdouridine, hypoxanthine, thymine and methylguanine. Of these five, unusual bases pseudouridine and dihyrdouridine are most commonly found in the tRNA molecules.

8. What is the correct pair of the four segments (R1, R2, R3, and R4)?
a) R1 and R2, R3 and R4
b) R2 and R3, R1 and R4
c) R1 and R3, R2 and R4
d) R2 and R1, R3 and R4
View Answer

Answer: b
Explanation: For recombination to occur, the R2 segment of the Trp DNA molecule must recombine with R3 segment of the bottom DNA molecule. R1 segment of the top molecule must recombine with R4 segment of the bottom DNA molecule.

9. What is the resolution?
a) Exchange of DNA fragments
b) Heterochromatin structure formation
c) Regeneration of duplex DNA molecule
d) Cleavage of holiday junction
View Answer

Answer: c
Explanation: In the process of homologous recombination, DNA molecules are regenerated by the process of genetic exchange. This is known as the process of resolution.

10. Which two Uvr component molecules scan the DNA during nucleotide excision repair?
a) UvrB, UvrC
b) UvrC, UvrA
c) UvrD, UvrA
d) UvrA, UvrB
View Answer

Answer: d
Explanation: In nucleotide excision repair complex of two UvrA and UvrB molecules scan the DNA with two UvrA subunits being responsible for detecting the distortions to the helix. Upon encountering a distortion, UvrA exits the complex and create a single stranded bubble with UvrB.

11. In the following type of libraries pick the odd one out.
a) cDNA library
b) A DNA library
c) Z DNA library
d) B DNA library
View Answer

Answer: a
Explanation: cDNA library lacks DNA fragments from the genomic DNA. This type of library is produced by the action of reverse transcriptase on the mRNA molecule to synthesize complementary DNA molecules without the intervening introns.

12. Which of the following parts of the mRNA determines the specificity of the amino acid attached?
a) Acceptor stem
b) D loop
c) ΨU loop
d) Variable loop
View Answer

Answer: a
Explanation: Genetic, biochemical and X-ray crystallographic evidence indicate that the specificity determinants are clustered at the two distant sites on the molecule. They are the acceptor stem and the anticodon loop.

13. Which of the following is not true about nucleotides?
a) Energy rich molecules
b) Monomeric units
c) Ubiquitous substances
d) Non enzymatic molecules
View Answer

Answer: d
Explanation: The nucleotides are known to be enzymatic molecules. For example, ribozymes are catalytic molecules. Also certain derivatives of nucleotides such as ATP, coenzyme A, nicotinamide adenine dinucleotide, etc., are important catalytic molecules that participate in various enzymatic processes.

14. Which of the following is wrongly paired?
a) Nucleic acid – hydrogen bond
b) Polysaccharide – glycosidic bond
c) Proteins – peptide bond
d) Phospholipids –phosphate linkage
View Answer

Answer: a
Explanation: Nucleic acids, that is, DNA and RNA show phosphodiesterase linkage which is the major type of linkage. Without the phosphodiester bonds between the phosphate and adjacent 3’OH sugar molecule the backbone will not be formed. Therefore, the nucleotides would not be able to attach and bond to form a nucleic acid.
advertisement

15. Which of the following factors do not provide to the separation of DNA fragments during electrophoresis?
a) Size
b) Matrix density
c) Chargaff’s rule
d) Ethidium bromide
View Answer

Answer: d
Explanation: Ethidium bromide only helps in tagging the DNA molecules to make the visible under the UV radiation due to its fluorescence property, but does not take any part in the separation of DNA molecules during electrophoresis.

16. Which of the following is the slowest process among the following?
a) Splicing
b) Translation
c) Transcription
d) Replication
View Answer

Answer: b
Explanation: The speed of DNA replication that is, 200 to 1000 nucleotides per second. Translation takes place at a rate of only 2 to 20 amino acids per second.

17. Which of the following function of DNA is necessary for the purpose of evolution?
a) Mutation
b) Replication
c) Translation
d) Transcription
View Answer

Answer: a
Explanation: Mutation facilitates the change of bases within a DNA and if this change encodes for a viable amino acid which in turn may lead to the synthesis of a different protein. This protein exerts a phenotypic character to the organism which may be different from the wild type character or may generate a unique character itself, thus leading to evolution.

18. Which of the following is not a component of the nucleic acid backbone?
a) Nucleotide
b) Phosphate group
c) Pentose sugar
d) Phosphodiesterase bond
View Answer

Answer: a
Explanation: A nucleic acid backbone is mainly composed of a pentose-phosphate unit which acts as a monomer. The repeat of this monomer is attached together by the phosphodiesterase linkage, thus, giving rise to the backbone. The nucleotides attached to the sugar moieties forms the side chain which gives rise to the hydrogen linkage with its complementary strand.

19. Which of the following does not take part in gene expression?
a) Transcription
b) RNA processing
c) Replication
d) Translation
View Answer

Answer: c
Explanation: Replication is the coping of the gene in double but plays no role in the production of protein thus, expression of gene. Transcription is the production of RNA from DNA and RNA processing is used for stabilizing the RNA in cytosol ad excision of non-coding regions. Translation is the major process that leads to the formation of polypeptide chain.
advertisement

20. Which of the following is a character of ORF?
a) Non – overlapping
b) 3 – nucleotide codons
c) Contiguous
d) Intron
View Answer

Answer: d
Explanation: Exons are the part of nascent RNA that are connected together to form RNA after the removal of introns by the splicosome. The splicosome in the complex formed in the nucleus with nascent RNA being the substrate for the formation of mature RNA after its splicing and other post transcriptional mechanisms.

21. Which of the following does not contribute to the stability of tRNA?
a) Hydrogen bonding
b) Hydrophobic interactions
c) Base and sugar-phosphate backbone interaction
d) Base pairing
View Answer

Answer: b
Explanation: Due to the negative charge of the tRNA backbone, it is unlikely for the molecule to have a hydrophobic nature. Thus, hydrophobic interactions do not play any role in the structural stability of the molecule. On the other hand, the other interactions such as the hydrogen bonding lead to base pairing which leads to its classic clover leaf model.

22. Which histone molecule produces novel binding sites for protein components of the kinetochore?
a) H3
b) H4
c) H2A
d) CENP – A
View Answer

Answer: d
Explanation: A histone variant CENP – A, is associated with the nucleosome that include centromeric DNA. In this region CENP – A replaces H3 subunit in the nucleosomes. These nucleosomes are incorporated into the kinetochore which mediates attachment of the chromosome to the mitotic spindle. The extended tail of CENP – A may generate these novel binding sites for other binding protein components of the kinetochore.

23. Which of the following is not promoted by histone tail modification?
a) Nucleosome sliding
b) Nucleosome remodeling
c) Gene expression
d) Formation of repressive structures
View Answer

Answer: a
Explanation: Nucleosome sliding is a type of Nucleosome remodeling. It is facilitated by Nucleosome remodeling complex. It cannot be promoted alone by modifying histone tail unless a nucleosome remodeling complex comes along.

24. Which of these factors contribute to a decrease in gene density?
a) Intergenic sequence
b) Cell size
c) Operon
d) Exon sequence
View Answer

Answer: a
Explanation: As the genome size increases the DNA between two consecutive sequences increase, known as the Intergenic sequences. Thus, with the increase in genome complexity, regulatory sequences are required for the proper functioning of the different mechanisms. These regulatory sequences are stored in these Intergenic sequences.

25. Which of the following will form a palindromic sequence?
a) AGTCCTGA
b) GTTCCAAG
c) ATTGCAAT
d) GTTGGAAC
View Answer

Answer: c
Explanation: The complementary sequence of ATTGCAAT is TAACGTTA. Thus, when the first is read from left to right and the later read from right to left the sequence of the bases is exactly the same. This is the criteria for a sequence to be palindromic.

26. Which of the following cannot be used for the separation of nucleic acids?
a) Northern blotting
b) PAGE
c) SDS – PAGE
d) None of the mentioned
View Answer

Answer: c
Explanation: Sodium dodecyl sulphate is a detergent, often used in biochemical preparations, binds to proteins and causes them to form a rod like structure. Most proteins bind SDS in the same ratio (1.4g per g of protein). Thus, the electrophoresis of proteins in an SDS – containing polyacrylamide gel separates them in order of their molecular masses. It is not known to have a similar effect on nucleic acids.

27. Which of the following organism has been found to have a positively supercoiled DNA?
a) Thermus aquaticus
b) Saurida tumbil
c) Monarda didyma
d) Cyanobacteria
View Answer

Answer: a
Explanation: The only organisms that are found to have positively supercoiled DNA are certain thermophiles, microorganisms living under conditions of extremely high temperature. Example of one such bacteria found in hot springs are Thermus aquaticus.

28. Which of the following does not occur during cell division in prokaryotes?
a) DNA rejoining
b) Strand passage
c) Multiple decatenations
d) DNA cleavage
View Answer

Answer: c
Explanation: Between the steps of DNA cleavage and DNA rejoining, the topoisomerase promotes the passage of a second segment of DNA through the break. Topoisomerase function thus involves DNA cleavage, strand passage and DNA rejoining in highly coordinated manner.

29. During DNA cloning which of the following is not a crucial requirement?
a) Protein expression
b) Vector
c) Molecular cutter
d) DNA inserts
View Answer

Answer: a
Explanation: DNA cloning typically involves a vector that carried the DNA insert into a host cell. Molecular cutters are important to incorporate the DNA insert into the vector thus giving rise to the chimera molecule. Hence cloning is complete if the organism replicates and the DNA insert replicates along with it.

30. Which of the following is not required for DNA sequencing?
a) Polymerase chain reaction
b) Electrophoresis
c) Restriction digestion
d) Cloning
View Answer

Answer: d
Explanation: DNA sequencing is the process of determining the precise order of nucleotides within a DNA molecule. It includes the methods and technologies of restriction endonuclease, electrophoretic techniques and Polymerase Chain Reaction.

31. Though unusual, pre – tRNA also undergo splicing. Which of the following helps in achieving this?
a) tRNA itself
b) Endonuclease
c) Splicosome
d) RNA polymerase exonuclease activity
View Answer

Answer: b
Explanation: Though unusual, pre – tRNA and pre – rRNAs also undergo splicing. In contrast to other splicing reactions, which involve the activity of catalytic RNAs, tRNA splicing is mediated by conventional protein enzymes. An endonuclease cleaves the pre – tRNA at the splice site to excise the intron, followed by the joining of the exons to form a mature tRNA molecule.


Chapterwise Multiple Choice Questions on Molecular Biology

Molecular Biology MCQ - Multiple Choice Questions and Answers

Our 1000+ MCQs focus on all topics of the Molecular Biology subject, covering 100+ topics. This will help you to prepare for exams, contests, online tests, quizzes, viva-voce, interviews, and certifications. You can practice these MCQs chapter by chapter starting from the 1st chapter or you can jump to any chapter of your choice.
  1. DNA, RNA and Protein
  2. Genomes and DNA
  3. Manipulation of Nucleic Acids & Polymerase Chain Reaction
  4. DNA Sequencing
  5. DNA Replication
  6. Transcriptions of Genes
  7. Expression of Genetic Information
  8. Processing of RNA
  9. Protein Synthesis
  10. Regulation of Transcription in Prokaryotes
  11. Mobile DNA
  12. Plasmids
  13. Manipulation of Genetic Material
  14. Mutations and Repair
  15. Recombination

1. Molecular Biology MCQ on DNA, RNA and Protein

The section contains molecular biology multiple choice questions and answers on dna history as genetic material, nucleic acids chemical structures, double stranded dna forms, central dogma outlines, ribosomes read the genetic code and rna classes having different functions.

  • History of DNA as the Genetic Material, Nucleic Acid Molecules Genetic Information
  • Chemical Structures of Nucleic Acids
  • Double Stranded DNA Forms a Double Helix
  • The Central Dogma Outlines the Flow of Genetic Information
  • Ribosomes Read the Genetic Code
  • Various Classes of RNA Have Different Functions – 1
  • Various Classes of RNA Have Different Functions – 2
  • 2. Molecular Biology Multiple Choice Questions on Genomes and DNA

    The section contains molecular biology questions and answers on genome organization, eukaryotic dna features, palindromes, inverted repeats and stem and loop structures, dna fragments separation by electrophoresis, dna helical structures, dna topology, chromatin centromere and telomere.

  • Genome Organization – 1
  • Genome Organization – 2
  • Genome Organization – 3
  • Repeated Sequences are a Feature of Eukaryotic DNA
  • Palindromes, Inverted Repeats and Stem and Loop Structures
  • Separation of DNA Fragments by Electrophoresis
  • Alternative Helical Structures of DNA
  • DNA Topology – 1
  • DNA Topology – 2
  • DNA Topology – 3
  • Chromatin Centromere and Telomere
  • 3. Molecular Biology MCQ on Manipulation of Nucleic Acids & Polymerase Chain Reaction

    The section contains molecular biology MCQs on dna manipulation, dna and rna hybridization, pcr fundamentals, inverse pcr, randomly amplified polymorphic dna and reverse transcriptase pcr.

  • Manipulating DNA
  • Hybridization of DNA and RNA
  • Fundamentals of PCR
  • Inverse PCR, Randomly Amplified Polymorphic DNA(RAPD)
  • Reverse Transcriptase PCR
  • 4. Molecular Biology Multiple Choice Questions on DNA Sequencing

    The section contains molecular biology multiple choice questions and answers on chain termination sequencing principles and automated sequencing.

  • General Principles for Chain Termination Sequencing
  • Automated Sequencing
  • 5. Molecular Biology MCQ on DNA Replication

    The section contains molecular biology questions and answers on dna replication occurs at the replication fork, dna polymerase properties, nucleotides are the precursors for dna synthesis, replication form complex, replicon concept, replicating linear dna in eukaryotes, chromosome replication initiates at oric & terminates at terc.

  • DNA Replication Occurs at the Replication Fork
  • Properties of DNA Polymerase – 1
  • Properties of DNA Polymerase – 2
  • Nucleotides are the Precursors for DNA Synthesis
  • DNA Polymerase Elongates DNA Strands, Complete Replication Form Complex
  • Chromosome Replication Initiates at OriC & Terminates at TerC
  • The Concept of the Replicon
  • Replicating Linear DNA in Eukaryotes
  • 6. Molecular Biology Multiple Choice Questions on Transcriptions of Genes

    The section contains molecular biology MCQs on genes expression by making rna, gene recognized beginning, rna polymerase and message manufacturing.

  • Genes are Expressed by Making RNA – 1
  • Genes are Expressed by Making RNA – 2
  • How Is the Beginning of a Gene Recognized
  • Manufacturing the Message – 1
  • Manufacturing the Message – 2
  • RNA Polymerase Knows Where to Stop
  • 7. Molecular Biology MCQ on Expression of Genetic Information

    The section contains molecular biology multiple choice questions and answers on genetic code, rna viruses and reverse transcription.

  • The Genetic Code – 1
  • The Genetic Code – 2
  • RNA Viruses and Reverse Transcription
  • 8. Molecular Biology Multiple Choice Questions on Processing of RNA

    The section contains molecular biology questions and answers on rna processing, coding and non coding rna, ribosomal processing, eukaryotic messenger, introns removal from rna by splicing,alternative splicing forms and mRNA degradation.

  • RNA Is Processed in Several Ways
  • Coding and Non-Coding RNA
  • Processing of Ribosomal and Transfer RNA
  • Eukaryotic Messenger RNA Contains a Cap and a Tail
  • Introns are Removed from RNA by Splicing – 1
  • Introns are Removed from RNA by Splicing – 2
  • Introns are Removed from RNA by Splicing – 3
  • Alternative Splicing Produces Multiple Forms of RNA
  • Degradation of mRNA
  • 9. Molecular Biology MCQ on Protein Synthesis

    The section contains molecular biology MCQs on protein synthesis overview, amino acids chains, cells decoding machine, three possible reading frames exist, tRNA occupies three sites during elongation of the polypeptide, protein synthesis mistranslation, proteins post translational modifications and degradation.

  • Overview of Protein Synthesis – 1
  • Overview of Protein Synthesis – 2
  • Proteins are Chains of Amino Acids
  • The Ribosome : The Cell’s Decoding Machine – 1
  • The Ribosome : The Cell’s Decoding Machine – 2
  • Three Possible Reading Frames Exist
  • The tRNA Occupies Three Sites During Elongation of the Polypeptide
  • Differences Between Eukaryotic and Prokaryotic Protein Synthesis, Mistranslation in Protein Synthesis
  • Post Translational Modifications of Proteins
  • Degradation of Proteins
  • 10. Molecular Biology Multiple Choice Questions on Regulation of Transcription in Prokaryotes

    The section contains molecular biology multiple choice questions and answers on gene regulation, regulation levels, activators and repressors in positive and negative regulation, transcriptional regulation in eukaryotes, methylation of eukaryotic dna controls gene expression, x-chromosomes inactivation and rnas in gene regulation.

  • Gene Regulation Ensures a Physiological Response
  • Regulation at the Level of Transcription Involves Several Steps
  • Activators and Repressors Participate in Positive and Negative Regulation
  • Transcriptional Regulation in Eukaryotes is More Complex than in Prokaryotes – 1
  • Transcriptional Regulation in Eukaryotes is More Complex than in Prokaryotes – 2
  • RNAs in Gene Regulationv
  • Methylation of Eukaryotic DNA Controls Gene Expression – 1
  • Methylation of Eukaryotic DNA Controls Gene Expression – 2
  • X-Chromosomes Inactivation Occurs in Female XX Animals
  • 11. Molecular Biology MCQ on Mobile DNA

    The section contains molecular biology questions and answers on mobile dna elements and multitude of transposable elements.

  • Most Mobile DNA Consists of Transposable Elements
  • The Multitude of Transposable Elements – 1
  • The Multitude of Transposable Elements – 2
  • 12. Molecular Biology Multiple Choice Questions on Plasmids

    The section contains molecular biology MCQs on plasmids properties, plasmid dna replicates by two alternative methods, transferring ti plasmids from bacteria to plants and plasmids helping their host cells.

  • General Properties of Plasmids
  • Plasmid DNA Replicates by Two Alternative Methods – 1
  • Plasmid DNA Replicates by Two Alternative Methods – 2
  • Many Plasmids Help their Host Cells
  • Ti Plasmids are Transferred from Bacteria to Plants – 1
  • Ti Plasmids are Transferred from Bacteria to Plants – 2
  • 13. Molecular Biology MCQ on Manipulation of Genetic Material

    The section contains molecular biology multiple choice quesions and answers on engineered genes and their uses, dna and rna libraries construction.

  • Construction of DNA and RNA Libraries
  • Engineered Genes and Their Use
  • 14. Molecular Biology Multiple Choice Questions on Mutations and Repair

    The section contains molecular biology questions and answers on genetic mutations, chemical mutagens damaging dna, dna repair overview and site directed mutagenesis.

  • Types of Genetic Mutations
  • Chemical Mutagens Damage DNA
  • Overview of DNA Repair
  • Site-Directed Mutagenesis
  • 15. Molecular Biology Multiple Choice Questions on Recombination

    The section contains molecular biology MCQs on molecular basics of homologous recombination, site specific recombination and higher organisms recombination.

  • Molecular Basis of Homologous Recombination
  • Site – Specific Recombination
  • Recombination in Higher Organisms – 1
  • Recombination in Higher Organisms – 2
  • If you would like to learn "Molecular Biology" thoroughly, you should attempt to work on the complete set of 1000+ MCQs - multiple choice questions and answers mentioned above. It will immensely help anyone trying to crack an exam or an interview.

    Wish you the best in your endeavor to learn and master Molecular Biology!

    advertisement
    Manish Bhojasia - Founder & CTO at Sanfoundry
    Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

    Subscribe to his free Masterclasses at Youtube & discussions at Telegram SanfoundryClasses.