Category: Objective Questions

Molecular Biology Interview Questions on “Genome Organization – 3”.

1. Which of the following facilitates nucleosome positioning?
A. Nucleosome remodeling complex
B. Topoisomerase II
C. SMC protein
D. DNA – binding protein

Answer: D
Explanation: Nucleosome positioning can be directed by DNA – binding protein or particular DNA sequences. Just as many proteins cannot bind to DNA within the nucleosome, prior binding of a protein to a site on DNA can prevent association of the core histone with that stretch of DNA. If two such DNA – binding proteins are bound to sites closer than the minimal nucleosomal DNA requirement (≈150 bp) the DNA stretch between the two proteins will remain nucleosome free.

2. Which of the following regions promote histone – DNA association?
A. A, T
B. A, G
C. G, C
D. C, T

Answer: A
Explanation: A:T rich DNA has an intrinsic tendency to bend toward the minor grove. Thus A:T rich DNA is favored in positions in which the minor grove faces the histone octamer. G:C rich DNA has the opposite tendency thus, is favored when the major grove faces away from the histone octamer.

3. With respect to end terminal modification of the histone tail which of the following options is true?
A. Lysine – phosphate modification
B. Serine – methylation
C. Acetylation – transcriptionally active
D. Modifications – involvement in gene expression

Answer: D
Explanation: Acetylation marks transcriptionally active region whereas methylation marks both transcriptionally active and repressed regions. Finally, phosphorylation histone H3 is commonly seen in highly condensed chromatin. Thus, these modifications result in a code that can be read by the proteins involved in gene regulation and expression.

4. Which of the following is a function of a modified histone tail?
A. Association with adjacent nucleosome
B. Interaction with DNA backbone
C. Interaction with chromodomains
D. Formation of 40-fold DNA structure

Answer: C
Explanation: Modification of histone tail generates binding sites for proteins. Specific protein domains called bromodomains and chromodomains mediate these interactions. Chromodomains containing proteins interact with methylated histone tails and are generally associated with tail specific methylating enzymes.

5. Bromodomains of proteins are associated with phosphorylated histone tails.
A. True
B. False

Answer: B
Explanation: Bromodomains of proteins interacts with the acetylated histone tails. These proteins are generally associated with histone tail – specific acetyl transferases. Such complexes facilitate the maintenance of acetylated chromatin by further modifying the already acetylated regions.

6. Which of the following enzymes of transcription commonly contains a bromodomain?
A. TFIID
B. CDK
C. Pre – RC
D. DNA polymerase

Answer: A
Explanation: Bromodomain containing proteins are involved in regulating transcription or formation of heterochromatin. Only TFIID of the above options is involved in transcription of DNA whereas the others are involved in DNA replication.

7. Which of the following enzymes is not correctly paired with its function?
A. Acetyl transferase – adds acetyl group to lysine
B. Methyl transferase – adds methyl group to serine
C. Topoisomerase – associated with nuclear scaffold
D. Deacetylases – removes acetyl groups from serine

Answer: B
Explanation: Methylation is an N – terminal modification of histone tail induced by the enzyme methyl transferase. But methylation is induced in the amino acid lysine. Serine is generally involved with phosphorylation.

8. Which of the following is not promoted by histone tail modification?
A. Formation of repressive structures
B. Gene expression
C. Nucleosome remodeling
D. Nucleosome sliding

Answer: D

Molecular Biology Multiple Choice Questions on “DNA Replication Occurs at the Replication Fork”.

1. Semiconservative nature of replication of eukaryotic chromosome was first demonstrated by _______________
A. Walter Flemming on root tip cells of Vicia faba
B. J. Herbert Taylor, Philip Wood and Walter Hughes on root tip cells of Vicia faba
C. Walter Flemming on root tip cells of Phaseolus vulgaris
D. J. Herbert Taylor, Philip Wood and Walter Hughes on root tip cells of Phaseolus vulgaris

Answer: B
Explanation: Walter Flemming discovered cell division not semi conservative nature of replication. Semiconservative nature of replication was first demonstrated by J. Herbert Taylor, Philip Wood and Walter Hughes on root tip cells of broad bean which is the common name for Vicia faba.

2. Pick the correct pair with respect to primers used in DNA replication.
A. RNA primer- for prokaryotes only
B. DNA primer-for eukaryotes only
C. DNA primer- for both prokaryotes and eukaryotes
D. RNA primer- for both prokaryotes and eukaryotes

Answer: D
Explanation: Short oligonucleotides of RNA are required by DNA polymerase for the synthesis of both leading and lagging strands of DNA due to the requirement of free 3’ end for DNA synthesis. As formation of oligonucleotides of DNA by DNA polymerase also requires a free 3’ end thus, DNA primers are not applicable for the synthesis of new strands of DNA during replication.

3. Which of the following is correctly matched with its subsequent role?
A. Topoisomerase II- can remove both positive and negative supercoil in the DNA duplex
B. Polymerase I- larger fragment responsible for exonuclease activity
C. DnaA protein- responsible for “melting” of the DNA double helix during replication
D. DnaB protein- attaches to the newly unwounded single strand of DNA to prevent folding of the strand

Answer: C
Explanation: The reasons are
i) Topoisomerase II- converts a positive supercoil to a negative supercoil, also known as gyrase
ii) Polymerase I- larger (klenow) fragment is responsible for polymerase activity
iii) DnaB protein- also known as helicase helps in unwinding of DNA duplex to form the open complex.

4. Replication fork is the junction between the two ___________
A. Unreplicated DNA
B. Newly synthesized DNA
C. Newly separated DNA strands and newly synthesized DNA strands
D. Newly separated DNA strands and the unreplicated DNA

Answer: D
Explanation: As both the strands of DNA occur simultaneously the two template strands undergo separation. The junction between the newly separated DNA strands and the unreplicated DNA is known as the replication fork.

5. Which of the following does not affect DNA replication?
A. Antiparallel nature of DNA
B. End specificity of polymerase
C. SSB protein
D. Helicase

Answer: C
Explanation: The antiparallel nature of DNA and end specificity of polymerase of polymerase leads to two types of strand synthesis, leading and lagging strands. Helicase helps in the unwinding of the DNA helix. SSB protein binds to the single stranded DNA during replication to stabilize it but does not take any part in new strand synthesis.

6. Who was the first person to analyse the process of replication and on which organism?
A. Arthur Kornberg: E. coli
B. John Cairns: E. coli
C. Arthur Kornberg: Bacillus subtilis
D. John Cairns: Bacillus subtilis

Answer: B
Explanation: The person who first analyzed the process of replication was John Cairns in which E. coli were grown in the presence of radioactive Thymidine. This allowed subsequent visualization of newly replicated DNA by autoradiography.

7. In the case of a circular DNA synthesis how many replication forks are observed?
A. 1
B. 2
C. 3
D. 4

Answer: B
Explanation: In case of replication of a complete circular DNA molecule 2 replication forks are observable. This represents the regions of active DNA synthesis and is represented in form of a bubble known as the replication bubble.

8. Primer synthesis short stretches of DNA for replication.
A. True
B. False

Answer: B
Explanation: Primer synthesizes short stretches of RNA for replication. These RNA serves as primers for the synthesis of both the leading and lagging strand during replication.

9. Which of the following is not used for degrading RNA from RNA:DNA hybrid in replication?
A. RNase A
B. RNase H
C. Polymerase I
D. Exonuclease

Answer: A
Explanation: RNase H dissolves RNA in eukaryotes and the last rNTP connected directly to the dNTP is digested by exonuclease. Polymerase I hydrolyses RNA in the 5’ – 3’ direction in prokaryotes. RNase A is not required in replicative purpose.

10. The gaps formed by the hydrolyzing the RNA from RNA:DNA hybrid is filled by DNA polymerase I and the nicks are ligated by T4 ligase.
A. True
B. False

Answer: B
Explanation: The gaps formed by the hydrolyzing the RNA from RNA:DNA hybrid is filled by DNA polymerase δ. The nicks are then filled in by T4 ligase at the cost of an ATP yielding an intact lagging strand.

11. Which of the following is correctly matched with its subsequent role?
A. Topoisomerase II- can remove both positive and negative supercoil in the DNA duplex
B. Polymerase I- larger fragment responsible for exonuclease activity
C. DnaA protein- responsible for “melting” of the DNA double helix during replication
D. DnaB protein- attaches to the newly unwounded single strand of DNA to prevent folding of the strand

Answer: C

Molecular Biology Multiple Choice Questions on “RNA Viruses and Reverse Transcription”.

1. RNA genomes were first discovered in ___________ viruses.
A. Plant
B. Animal
C. Bacterial
D. Fungal

Answer: A
Explanation: RNA genomes were first discovered in the plant Tobacco mosaic virus. The first direct proof that RNA acts as the genetic material was obtained in 1950s by experiments demonstrating that RNA purified from TMV could infect new host cells giving rise to progeny viruses.

2. The initial hypothesis of RNA provirus was proposed by __________ in 1960s.
A. David Baltimore
B. Howard Temin
C. Robert Gallo
D. David J. Griffiths

Answer: B
Explanation: The initial hypothesis of RNA provirus was proposed by Howard Temin in 1960s. In his experiments he found that the RNA tumor viruses replicate via synthesis of DNA intermediates called DNA proviruses, thus leading to his hypothesis.

3. Reverse transcription is an important phenomenon for eukaryotic cells.
A. True
B. False

Answer: A
Explanation: Reverse transcription is not restricted to retroviruses it also occurs in cells. For example, reverse transcription is essential for the replication of telomeres of eukaryotic chromosomes. Also reverse transcription is responsible for the transposition of sequences from one position to the other.

4. The virus on which the first experiment performed by Howard Temin was __________
A. Human Immunodeficiency Virus
B. T lymphatic Virus
C. Rous Sarcoma Virus
D. Human papiloma virus

Answer: C
Explanation: Rous sarcoma virus (RSV) the first cancer causing virus to be described was of considerable interest as an experimental system for studying the molecular biology of cancer. Howard Temin began his research in this area when, as a graduate student in 1958, he developed the first assay for the transformation of normal cell to cancer cells in culture following infection with RSV.

5. The viral genome contains which of the following characteristic sequences?
A. LINE
B. SINE
C. Transposons
D. LTRs

Answer: D
Explanation: The viral genome contains the characteristic sequence of long terminal repeats (LTRs), which are direct repeats of several hundred base pairs. Viral genes including genes for reverse transcriptase, integrase and structural proteins of the virus particle, are located between the LTRs.

6. The integration of viral DNA into the host DNA is promoted by the host integrase enzyme.
A. True
B. False

Answer: B
Explanation: The viral DNA integrates into the host cell chromosome by a process that resembles the integration of DNA transposable elements. This integration is catalyzed by a viral integrase and occurs at many different target sequences of the host chromosome.

7. Which of the following is not a function of reverse transcriptase?
A. RNA dependent DNA polymerase
B. DNA dependent DNA polymerase
C. RNase H
D. Exonuclease

Answer: D
Explanation: Reverse transcription has a high error rate due to no proofreading activity. Thus the reverse transcriptase that facilitates reverse transcription has no exonuclease activity.

8. Reverse transcription has a high error rate.
A. True
B. False

Answer: A
Explanation: As the reverse transcriptase has no exonuclease activity thus, proofreading of the synthesized cDNA is not possible. This accounts to the high error rate of 1.7*10-4 of reverse transcription.

9. What will be the transcription product of 3’….AUCCGAGCUAAC….5’ by reverse transcriptase?
A. 3’….GTTAGCTCGGAT….5’
B. 3’….AUCCGAGGAUUG….5’
C. 5’….GTTAGCTCGGAT….3’
D. 5’….UAGGCUCGAUUG….3’

Answer: A
Explanation: The reverse transcriptase facilitates reverse transcription from RNA to DNA. The given sequence in the question is of RNA as it consists of “U” instead of “T” thus the resulting cDNA sequence should be 3’….AUCCGAGCUAAC….5’5’….TAGGCTCGATTG….3’.

10. Reverse transcription is a very important tool in modern molecular biology techniques.
A. True
B. False

Answer: A

Basic Molecular Biology Questions on “The tRNA Occupies Three Sites During Elongation of the Polypeptide”.

1. For the correct addition of amino acid to the growing polypeptide chain which of the following does not play any role?
A. Loading of initiator tRNA to the P site
B. Loading of correct aminoacyl tRNA to the A site
C. Formation of peptide bond between the existing amino acid and the incoming amino acid
D. The formed tRNA with the growing polypeptide is translocated from the A site to the P site

Answer: A
Explanation: The correct addition of amino acid involves only three steps:
i) Loading of correct aminoacyl tRNA to the A site
ii) Formation of peptide bond between the existing amino acid and the incoming amino acid
iii) The formed tRNA with the growing polypeptide is translocated from the A site to the P site
Loading of the initiator tRNA is the part of initiation of translation process.

2. The events controlling the correct addition of amino acid is controlled by ____________ proteins.
A. 1
B. 2
C. 3
D. 4

Answer: B
Explanation: The events controlling the correct addition of amino acid are controlled by 3 proteins known as elongation factors. They are IF1, IF2 and IF3.

3. The auxillary protein required for the elongation of polypeptide is energy independent.
A. True
B. False

Answer: B
Explanation: The auxillary protein required for the elongation of polypeptide is energy dependent processes. All these factors use energy of the GTP binding and hydrolysis to enhance the rate and accuracy of ribosome function.

4. Aminoacyl tRNA needs an escort to carry them to the ribosome bound mRNA.
A. True
B. False

Answer: A
Explanation: Aminoacyl-tRNAs do not bind to the ribosome on their own. Instead, they are escorted to the ribosome by the elongation factor EF-Tu.

5. Once the tRNA is aminoacylated, EF-Tu binds to the tRNA at the ____________
A. 5’ end of the tRNA
B. 3’ end of the tRNA
C. Amino acid
D. Variable loop of tRNA

Answer: B
Explanation: Once the tRNA is aminoacylated, EF-Tu binds to the tRNA at the3’ end of the tRNA, masking the coupled amino acid. This interaction prevents the bound aminoacyl-tRNA from participating in peptide bond formation until it is released from EF-Tu.

6. The activation of GTPase activity of the enzyme EF-Tu occurs after its binding to the aminoacylated tRNA.
A. True
B. False

Answer: B
Explanation: The trigger h the factor binding center after the tRNA is loaded into that activates the EF-Tu GTPase id known as factor binding center. EF-Tu only interacts with the factor binding center after the tRNA is loaded into the A site and a correct codon-anticodon match is made. At this point, EF-Tu hydrolyzed its bound GTP and is released from the ribosome.

7. The only fidelity testing of the translation is by observing the energy difference involved in the correct and incorrect base pairing.
A. True
B. False

Answer: B
Explanation: The energy difference between a correctly formed codon-anticodon pair and that of a near match is not equal but still cannot account for the high level of accuracy required for the translation process. Thus there are three more mechanisms that contribute to this specificity. In each case, these mechanisms select against incorrect codon-anticodon pairings.

8. How many mechanisms are involved in the maintenance of the fidelity of translation?
A. 1
B. 2
C. 3
D. 4

Answer: D
Explanation: A total of 4 mechanisms are involved in the maintenance of the fidelity of translation. In addition to the codon-anticodon interactions, the ribosome exploits minor grove interactions and two phases of proof reading to ensure that a correct aminoacyl-tRNA binds in the A site.

9. Which part of the large subunit helps in the formation of the peptide bond?
A. 5S rRNA
B. Proteins
C. 23S rRNA
D. 18S rRNA

Answer: C
Explanation: Once the correctly charged tRNA has been placed in the A site and has rotated into the peptidyl transferase center, peptide bond formation takes place. This reaction is catalyzed by RNA, specifically the 23S rRNA component of the large subunit.

10. Which of the following steps is not required for the process of translocation?
A. Frame shift in hybrid states
B. Movement of P site tRNA to E site
C. Movement of A site tRNA to P site
D. Movement of ribosome by three nucleotides

Answer: A
Explanation: For a new round of peptide chain elongation to occur, the P site tRNA must move to the E site and the A site tRNA must move to the P site. At the same time, the mRNA must move by 3 nucleotides to expose the next codon. These movements are coordinated within the ribosome and are collectively referred to as translocation.

11. The completion of translocation requires the action of the factor _________________
A. EF-Tu
B. EF-G
C. eIF2
D. eIF4G

Answer: B

Molecular Biology Multiple Choice Questions on “General Properties of Plasmids”.

1. Plasmid replication is dependent on the host cell.
A. True
B. False

Answer: B
Explanation: The plasmid is an autonomous replicating genetic material. It has its own origin of replication and complete replicating machinery thus can replicate freely and is thus independent of the replication of the host genome.

2. How the plasmid clones can be screened?
A. By selectable markers
B. By bacterial resistance gene
C. For restriction site
D. By ARS sequence

Answer: A
Explanation: Plasmid contains a selectable marker that allows cells that contain the vector to be easily identified. Thus selectable markers are used to screen clones.

3. How many restriction sites are contained by a plasmid?
A. 1
B. 2
C. 3
D. More than 1

Answer: D
Explanation: Plasmid has one or more than one site for one or more restriction enzymes. Artificial plasmids contain a single restriction site for one or more restriction enzymes. This allows DNA fragments to be inserted at a definite position.

4. Who were the scientists who discovered the plasmid pBR322?
A. Rodriguez and Bolivar
B. Joller smith
C. Herbert Boyer
D. Stanley Cohen and Joller smith

Answer: A
Explanation: Plasmids are most commonly used as vector DNA. pBR322 is a plasmid vector discovered by Rodriguez and Bolivar in 1977.

5. Under relaxed conditions how many copies of plasmid are present in the cell?
A. 10 – 100 copies
B. 100 – 500 copies
C. 1 – 300 copies
D. 10 – 700 copies

Answer: D
Explanation: Most plasmids used in molecular cloning are generally present under relaxed conditions. They are normally present in 10 to as many as 700 copies per cell.

6. What is the length of the polylinker segment of plasmid?
A. Less than 100 base pair
B. Less than 10 base pair
C. Less than 70 base pair
D. Less than 50 base pair

Answer: A
Explanation: Plasmid vector contains a strategically located short, less than 100 base pair long segments of DNA. This segment of DNA is known as the polylinker segment.

7. The full for of pUC is polylinker university cloning.
A. True
B. False

Answer: B
Explanation: The E. coli derived plasmid.

8. The host bacterium takes up a plasmid in presence of ______________
A. Monovalent cations
B. Monovalent anions
C. Divalent cations
D. Divalent anions

Answer: C
Explanation: The host bacteria can take up a plasmid from its surrounding. This process is greatly enhanced by the presence of divalent cation such as Ca²⁺.

9. What is the temperature at which bacteria can takes up the plasmid?
A. 42˚C
B. -42˚C
C. 40˚C
D. -40˚C

Answer: B
Explanation: Bacteria efficiently take up the plasmid DNA at -42˚C. This increases cell membrane permeability to DNA.

10. Which gene in the pUC18 vector confers antibiotic resistance to the transformed cells?
A. LacZ
B. PvuII
C. AmpR
D. AntII

Answer: C
Explanation: pUC18 is a well-known cloning vector. It contains the AmpR gene that confers resistance to the antibiotic ampicillin which is used as a selectable marker.

11. What is the characteristic of lacZ gene of pUC18 vector among the following?
A. Encodes for antibiotic resistance
B. Encodes for β-galactosidase enzyme
C. Encodes for β-lactamase enzyme
D. Encodes for β-galactoside transferase enzyme.

Answer: B
Explanation: The lacZ gene of the pUC18 vector is a gene of the lac operon encoding for the β-galactosidase enzyme. This enzyme cleaves galactoside present in the medium as a carbon source and liberates a blue coloured product.

12. Which one of the following is the first engineered plasmid vector?
A. pBR322
B. pBR320
C. pUC18
D. pSC101

Answer: D
Explanation: Although pBR322 is the most commonly used vector in scientific research. pSC101 is the first engineered plasmid vector. The pUC family vectors are the derivative of the pBR family of vectors.

13. What is the expanded form of pBR in pBR322?
A. Plasmid Boliver and Rodriguez
B. Plasmid Baltimore and Rodriguez
C. Plasmid bacterial recombination
D. Plasmid bacterial replication

Answer: A
Explanation: pBR322 was the first artificial cloning vector developed in 1977 by Boliver and Rodriguez. Thus pBR represents its creators leading to the expansion- Plasmid Boliver and Rodriguez.

14. What is incorrect about plasmid?
A. Helps in reproduction
B. Contains stress resistant genes
C. Serves as the transformation vehicle
D. They are the genetic material of the bacteria

Answer: D
Explanation: Plasmids are the extra genetic materials that are found in the bacterial cell along with the genetic component. They are autonomously replicating cyclic double strand DNA molecules used as vectors for gene transfer and also for replication.

15. The repressor for the β-galactosidase gene is encoded by ___________
A. XmaI
B. PstI
C. Lac I
D. PvuII

Answer: C

Energy Engineering Multiple Choice Questions on “Necessity of a Steam Plant”.

1. Apart from geographical location, the amount of power generated in a country depends on ___________
A. Number of power producing plants
B. Annual consumption of power
C. Utilization of natural resources
D. Quantity of requirement

Answer: C
clarification: Since most of the power produced is from the natural resources, the estimation of amount of power generated in a country is made by the utilization of its natural resources. The ‘Annual consumption of power ‘would give you the details of power utilized for necessities, it is the amount of power utilized out of wholesome amount of total power produced in the country.

2. Total power generated is usually contributed by power generated through ____________
A. Hydel power plant, Thermal power plant and solar plant
B. Ocean thermal energy, Wind energy and Hydel power plant
C. Hydel power plant, Geo-thermal plant and Nuclear power plant
D. Hydel power plant, Thermal power plant and nuclear power plant

Answer: D
clarification: The energy or power produced from hydel power plant, thermal power plant and nuclear power plant is very abundant compared to any other combinations of power producing plants. All these three plants have ability to produce the power in thousands of megawatts in its own standards.

3. On what factors does hydel plant entirely depend?
A. Vegetation
B. Tropical cycle
C. Amount of Rainfall
D. Hydrological cycle
View Answer

Answer: D
clarification: Hydrological cycle is an explanation of the continuous movement of water above and below earth surface, where as rainfall is not reliable since it varies period to period. The amount of water above the earth surface and below the earth surface, both are responsible for the hydrological cycle. ‘Vegetation’ is info about the assemblage of plant species irrespective of their geographic characteristics.

4. The steam power plant serves as a base plant for ________
A. Nuclear power plant
B. Geothermal power plant
C. Thermal power plant
D. Diesel plant

Answer: A
clarification: Since power is generated by nuclear power plant and the nuclear plant needs power to perform its operations. For this purpose steam power plant is used as base power plant to generate this power. The power produced base plant acts as a fuel to run the nuclear power plant. And all the cost estimation to produce the electricity is made by considering base load expenses too.

5. What is the primary objective of a steam power plant?
A. To convert one form of energy into another form
B. To produce electricity
C. To provide employment
D. To serve as a base load plant to hydel plant or nuclear plant
View Answer

Answer: B
clarification: The primary objective of the steam power plant is to produce electricity and then serving as base load plant to hydel or nuclear power plant comes as second priority. Steam power plants produce 86% of electricity. And the efficiency of steam power plant is typically 33%-48%.

6. A steam power plant works on ___________ cycle.
A. Otto
B. Brayton
C. Hydrological
D. Rankine

Answer: D
clarification: Rankine cycle is a thermodynamic cycle of constant pressure engine that is to convert heat energy into mechanical work and from that following parts like adjoined blades and shafts are made to run to produce electricity. Otto cycle is used in automobile engine and Brayton cycle is used in heat engines & air jet engine.

7. Coal crushers are also known as__________
A. Lather
B. Coal combers
C. Feeder breakers
D. Coal washer
View Answer

Answer: C
clarification: Coal crushers are also known as feeder breakers since it is elaborated by the word itself. ‘Feeder’ depicts the following component coal being fed by the hoppers and ‘Breaker’ stands for breaking off into smaller pieces. And this synonym is rarely used.

8. Road transportation of coal is preferred for what type of usage?
A. Small capacity plant
B. Medium capacity plant
C. Large capacity plant
D. Domestic usage areas

Answer: A
clarification: Road transportation of coal is ideal transporting coal directly to point of consumption. These small capacity plants are usually located in the middle of land. Trucks and tippers are used to supply coal for this purpose. And also when the plant doesn’t have railway or shipway accessibility in such areas roadways are only possible means of transportation.

9. Which is the more economical way of transporting coal?
A. Sea or River ways
B. Railways
C. Road transporting
D. By Airlifting

Answer: B
clarification: We do know shipways are cheaper. But we need another mode of transport to transfer that coal to the plant area. But in case of railways the tracks can be made to directly pass through the plant. Hence the railway is more economical compared to any other means of transport.