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
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
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
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
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
Explanation: Ribonucleic acid (RNA) is a linear molecule made up of four different ribonucleotide bases: adenine (A), cytosine (C), guanine (G), and uracil (U).
6. Which of the following is a type of RNA involved in protein synthesis?
a) snRNA
b) rRNA
c) yRNA
d) dsRNA
View Answer
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
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
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
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
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
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
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
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
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.
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
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
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
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
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
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.
20. Which of the following is a character of ORF?
a) Non – overlapping
b) 3 – nucleotide codons
c) Contiguous
d) Intron
View Answer
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
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
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
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
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
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
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
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
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
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
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
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
- DNA, RNA and Protein
- Genomes and DNA
- Manipulation of Nucleic Acids & Polymerase Chain Reaction
- DNA Sequencing
- DNA Replication
- Transcriptions of Genes
- Expression of Genetic Information
- Processing of RNA
- Protein Synthesis
- Regulation of Transcription in Prokaryotes
- Mobile DNA
- Plasmids
- Manipulation of Genetic Material
- Mutations and Repair
- 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.
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.
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.
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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.
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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.
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.
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.
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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.
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.
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.
11. Molecular Biology MCQ on Mobile DNA
The section contains molecular biology questions and answers on mobile dna elements and multitude of transposable elements.
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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.
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.
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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.
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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.
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Wish you the best in your endeavor to learn and master Molecular Biology!
