NEET Previous Year Questions (2016-2024): Biotechnology: Principles & Processes | Biology Class 12 PDF Download

2024

Q1: Hind II always cuts DNA molecules at a particular point called recognition sequence and it consists of:    (NEET 2024)
(a) 8 bp
(b) 6 bp
(c) 4 bp
(d) 10 bp
Ans: (b)
The correct answer is option (2).
The first restriction endonuclease - Hind II, whose functioning depends on a specific DNA nucleotide sequence was isolated. It was found that Hind II always cut DNA molecules at a particular point by recognising sequence of six base pairs.
Option (1), (3) and (4) are incorrect because they have either more than 6 or less than 6bp.

Q2: What is the fate of a piece of DNA carrying only gene of interest which is transferred into an alien organism?
A. The piece of DNA would be able to multiply itself independently in the progeny cells of the organism.
B. It may get integrated into the genome of the recipient.
C. It may multiply and be inherited along with the host DNA.
D. The alien piece of DNA is not an integral part of chromosome.
E. It shows ability to replicate.
Choose the correct answer from the options given below:       (NEET 2024)
(a) A and B only
(b) D and E only
(c) B and C only
(d) A and E only
Ans: (c)
Sol: When a piece of DNA carrying a gene of interest is transferred into an alien organism, its fate depends on several factors, including the mechanisms it has for replication, integration, and inheritance. Here is an analysis of each statement provided:

A. The piece of DNA would be able to multiply itself independently in the progeny cells of the organism.
This is incorrect unless the DNA contains an origin of replication that is compatible with the host cell's replication machinery.

B. It may get integrated into the genome of the recipient.
This is a likely scenario if the DNA has sequences that facilitate recombination with the host genome or if the host has natural mechanisms of DNA integration such as those observed in bacteria with transformation capabilities, or other eukaryotic organisms with similar processes.

C. It may multiply and be inherited along with the host DNA.
This statement can be true if the introduced DNA is replicated along with the host DNA, possibly through integration into the host genome or existence in the form of an episome that replicates independently yet synchronously with the host DNA.

D. The alien piece of DNA is not an integral part of chromosome.
This statement is generally accurate before integration. The introduced DNA, before integration, exists extrachromosomally and thus is not part of any chromosome, unless mechanisms are present for its integration into the host genome.

E. It shows ability to replicate.
This statement depends on specific sequences in the DNA, such as the origin of replication compatible with the host cell's machinery, mentioned in statement A. Without these, it will not replicate independently.

Given these explanations, the most accurate answer that describes the fate of the DNA in the recipient organism is: Option C: B and C only
'B' is correct as the DNA may integrate into the host genome, and 'C' is correct as the DNA might also multiply if replicated in sync with the host organism's DNA, particularly if it integrates or exists as an episome compatible with the host's cellular machinery.

Q3: The following diagram showing restriction sites in E. coli cloning vector pBR322. Find the role of ‘X’ and ‘Y’ genes :     (NEET 2024)

(a) The gene ‘X’ is responsible for resistance to antibiotics and ‘Y’ for protein involved in the replication of Plasmid.
(b) The gene ‘X’ is responsible for controlling the copy number of the linked DNA and ‘Y’ for protein involved in the replication of Plasmid.
(c) The gene ‘X’ is for protein involved in replication of Plasmid and ‘Y’ for resistance to antibiotics.
(d) Gene ’X’ is responsible for recognitions sites and ‘Y’ is responsible for antibiotic resistance.
Ans: (b)
Sol: Correct answer is option (2), because
'X' in the given diagram is ori while 'Y' is rop.
'X' which is ori is responsible for controlling the copy number of the linked DNA and 'Y' which is rop codes for protein involved in the replication of plasmid.
Options (1), (3) and (4) are incorrect as 'X' and 'Y' are not related to these functions.

Q4: The "Ti plasmid" of Agrobacterium tumefaciens stands for   (NEET 2024)
(a) Tumour inhibiting plasmid
(b) Tumor independent plasmid
(c) Tumor inducing plasmid
(d) Temperature independent plasmid
Ans: (c)
Sol: The correct answer is Option C: Tumor inducing plasmid.
The "Ti plasmid" is a type of plasmid (a small DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently) found in the bacterium Agrobacterium tumefaciens. This bacterium is known for its ability to transfer a segment of its DNA to a plant, integrating this DNA into the plant's genome, causing the plant to develop tumors, known as crown gall disease.
The term "Ti plasmid" stands for "Tumor inducing plasmid" because of its role in this process. When Agrobacterium tumefaciens infects a plant, the Ti plasmid transfers a portion of its DNA-known as T-DNA (transfer DNA)-into a random site in the plant's genome. The expression of genes in the T-DNA leads to the overproduction of certain growth hormones (auxins and cytokinins), which results in the formation of tumors on the plant.
Thus, Option C "Tumor inducing plasmid" most accurately describes the Ti plasmid's function of inducing tumor formation in infected plants. Options A, B, and D do not correctly describe the properties or functions of the Ti plasmid.

2023

Q1: Which of the following is not a cloning vector?       (NEET 2023)
(a) BAC
(b) YAC
(c) pBR322
(d) Probe
Ans: (d)
Option (d) is correct answer because a single stranded DNA or RNA tagged with a radioactive molecule is called a probe and it helps in the detection of mutated gene.
Option (b), (c) and (a) are not correct because YAC, BAC, pBR322 are vectors.

2022

Q1: Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).        (NEET 2022)
Assertion (A): Polymerase chain reaction is used in DNA amplification
Reason (R): The ampicillin resistant gene is used as a selectable marker to check transformation
In the light of the above statements, choose the correct answer from the options given below:
(a) Both (A) and (R) are correct but (R) is not the correct explanation of (A)
(b) (A) is correct but (R) is not correct
(c) (A) is not correct but (R) is correct
(d) Both (A) and (R) are correct and (R) is the correct explanation of (A)
Ans: (a)

• Both the statements are correct but the given reason is not the correct explanation. Polymerase chain reaction is used in DNA amplification.
• Ampicillin resistance gene is a selectable marker that helps to check transformation by selection of transformants.

Q2: Given below are two statements:        (NEET 2022)
Statement I: Restriction endonucleases recognise specific sequence to cut DNA known as palindromic nucleotide sequence.
Statement II: Restriction endonucleases cut the DNA strand a little away from the centre of the palindromic site.
In the light of the above statements, choose the most appropriate answer from the options given below:
(a) Both Statement I and Statement II are incorrect
(b) Statement I is correct but Statement II is incorrect
(c) Statement I is incorrect but Statement II is correct
(d) Both Statement I and Statement II are correct
Ans: (d)
Option (d) is the correct answer because both the statements I and II are correct. Each restriction endonuclease recognises a specific palindromic nucleotide sequences in the DNA. It will bind to the DNA and cut each of the two strands of double helix at specific points. Restriction enzymes cut the strand of DNA a little away from the centre of the palindrome site; but between the same two bases on the opposite strands. So both the statements I and II are correct. 

Q3: Which of the following is not a desirable feature of a cloning vector?        (NEET 2022)
(a) Presence of a marker gene
(b) Presence of single restriction enzyme site
(c) Presence of two or more recognition sites
(d) Presence of origin of replication 
Ans: (c)
Option (d) is the correct answer. Cloning vectors are the carriers of the desired gene in the host cell. The features desirable in a cloning vector are :-

• Presence of origin of replication
• Presence of marker genes
• Presence of very few, preferably single recognition site for the commonly used restriction enzymes

Q4: Which one of the following statement is not true regarding gel electrophoresis technique?      (NEET 2022)
(a) The process of extraction of separated DNA strands from gel is called elution.
(b) The separated DNA fragments are stained by using ethidium bromide.
(c) The presence of chromogenic substrate gives blue coloured DNA bands on the gel.
(d) Bright orange coloured bands of DNA can be observed in the gel when exposed to UV light.
Ans: (c)
Option (c) is the incorrect statement, as bright coloured bands of DNA can be observed in the gel when EtBr (Ethidium bromide) treated DNA is exposed to UV light.

Q5: Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : When a particular restriction enzyme cuts strand of DNA, overhanging stretches or sticky ends are formed.
Reason (R) : Some restriction enzymes cut the strand of DNA a little away from the centre of palindromic site.
In the light of the above statements, choose the correct answer from the options given below :
(a) (A) is not correct but (R) is correct
(b) Both (A) and (R) are correct and (R) is the correct explanation of (A)
(c) Both (A) and (R) are correct but (R) is not the correct explanation of (A)
(d) (A) is correct but (R) is not correct     (NEET 2022 Phase 2)
Ans: (b)
Option (b) is the correct answer because when restriction enzymes cut the strand of DNA a little away from the centre of the palindrome sites, but between the same two bases on the opposite strands, then single stranded portions are left at the ends. These overhanging stretches on each strand are called sticky ends.

Q6: Separation of DNA fragments is done by a technique known as     (NEET 2022 Phase 2)
(a) Gel electrophoresis
(b) Polymerase Chain Reaction
(c) Recombinant technology
(d) Southern blotting
Ans: (a)

• Option (1) is the correct answer because separation of DNA fragments which is carried out after restriction enzyme digestion, is done by a technique known as gel electrophoresis.
• Option (2) is not the correct answer because polymerase chain reaction (PCR) is a technique used for amplification of gene of interest.
• Option (3) is not the correct answer because recombinant DNA technology comprises altering genetic material outside an organism to obtain enhanced and desired characteristics in living organisms or as their products.
• Option (4) is not the answer because Southern blotting is a method used for detection of specific DNA sequences in samples.

Q7: The enzyme (a) is needed for isolating genetic material from plant cells and enzyme (b) for isolating genetic material from fungus. Choose the correct pair of options from the following :
(a) (a) Cellulase (b) Lipase
(b) (a) Cellulase (b) Protease
(c) (a) Cellulase (b) Chitinase
(d) (a) Chitinase (b) Lipase     (NEET 2022 Phase 2)
Ans: (c)

• Option (3) is the correct answer because cellulase is used to isolate genetic material from plant cells and chitinase is used to isolate genetic material from fungal cells.
• Option (2) is incorrect because protease is used for digestion of proteins.
• Option (1) and (4) are incorrect because lipase is used for the breakdown of lipids.

Q8: Match List-I with List-II :     (NEET 2022 Phase 2)

Choose the correct answer from the options given below:
(a) (a) - (ii), (b) - (iii), (c) - (iv), (d) - (i)
(b) (a) - (ii), (b) - (i), (c) - (iv), (d) - (iii)
(c) (a) - (i), (b) - (iii), (c) - (ii), (d) - (iv)
(d) (a) - (iv), (b) - (i), (c) - (iii), (d) - (ii)
Ans: (b)
Option (2) is the correct answer because

• Gene gun or biolistics is a direct gene transfer method suitable for plant cell.
• Gene therapy involves replacement of a faulty gene by a normal healthy gene.
• Gene cloning is done to make identical copies of a particular DNA molecule.
• Genome is the total DNA in the cells of an organism.

Q9: Pathogenic bacteria gain resistance to antibiotics due to changes in their :      (NEET 2022 Phase 2)
(a) Nucleoid
(b) Cosmids
(c) Plasmids
(d) Nucleus
Ans: (c)
Plasmid is small circular DNA outside the genomic DNA. The plasmid DNA confers certain unique phenotypic characters to the bacteria such as resistance to antibiotics.

Q10: Which of the following methods is not commonly used for introducing foreign DNA into the plant cell?
(a) Bacteriophages
(b) Agrobacterium mediated transformation
(c) Gene gun
(d) ‘Disarmed pathogen’ vectors    (NEET 2022 Phase 2)
Ans: (a)

• Option (a) is the correct answer because bacteriophages act as a cloning vector for bacterial cells, not the plant cells.
• Options (b), (c) and (d) are not the correct answers because Agrobacterium, gene gun and disarmed pathogens as vectors are used for introducing foreign DNA into the plant cells.

Q11:Refer to the following statements for agarose-gel electrophoresis:    (NEET 2022 Phase 2)
(a) Agarose is a natural polymer obtained from sea-weed.
(b) The separation of DNA molecules in agarose-gel electrophoresis depends on the size of DNA.
(c) The DNA migrates from negatively-charged electrode to the positively-charged electrode
(d) The DNA migrates from positively-charged electrode to the negatively-charged electrode.
Choose the most appropriate answer from the options given below :
(a) (b), (c) and (d) only
(b) (a) and (b) only
(c) (a), (b) and (c) only
(d) (a), (b) and (d) only
Ans: (c)

• Option (c) is the correct answer as the most commonly used matrix in gel electrophoresis is agarose which is a natural polymer extracted from sea weeds.
• In agarose gel electrophoresis, the DNA fragments separate (resolve) according to their size through sieving effect provided by the agarose gel.
• Since, DNA fragments are negatively charged molecules, they migrate towards the anode (positively-charged electrode) under an electric field through a medium/martix.

2021

Q1: During the purification process for recombinant DNA technology, addition of chilled ethanol precipitates out:         (NEET 2021)
(a) Histones
(b) Polysaccharides
(c) RNA
(d) DNA
Ans: (d)

• Various enzymes like protease, RNase, etc. are added to break down substances like proteins, RNA, etc. Once all these substances are broken down, DNA is left which is precipitated out by adding chilled ethanol.
• Ethanol has a lower dielectric constant than water, making it to promote ionic bond formation the Na+ (from the salt) and the PO−3 (from the DNA backbone), further, causing the DNA to precipitate.

Q2: Match List-I with List-II .        (NEET 2021)

Choose the correct answer from the options given below.
(a)

(b)

(c)

(d)
Ans: (c)

• Pomato is obtained as a result of protoplast fusion.
• Totipotency is a property of explant to develop into whole plant body during plant tissue culture.
• Virus free plants can be obtained through meristem culture.
• Somaclones are obtained by the process of micropropagation.

Q3: Which of the following is a correct sequence of steps in a PCR (Polymerase Chain Reaction)?        (NEET 2021)
(a) Extension, Denaturation, Annealing
(b) Annealing, Denaturation, Extension
(c) Denaturation, Annealing, Extension
(d) Denaturation, Extension, Annealing
Ans: (c)

• PCR stands for Polymerase Chain Reaction. It is a technique in which multiple copies of gene of interest is synthesised using two sets of primers and the enzyme DNA polymerase. The correct sequence of steps in a PCR (Polymerase Chain Reaction) are
• Denaturation In which the double-stranded template DNA is heated at 95°C to separate it into two single strands.
• Annealing In which the temperature is lowered to 50°C which enables the DNA primers to attach to the template DNA.
• Extension/Extending In which the temperature is raised and the new strand of DNA is made by the taq polymerase enzyme.
• These three stages are repeated 20-40 times, doubling the number of DNA copies each time.

Q4: Plasmid pBR322 has a PstI restriction enzyme site within gene amp^R that confers ampicillin resistance. If this enzyme is used for inserting a gene for β β-galactoside production and the recombinant plasmid is inserted in an E.coli strain,         (NEET 2021) 
(a) it will lead to the lysis of host cells.
(b) it will be able to produce a novel protein with dual abilities.
(c) it will not be able to confer ampicillin resistance to the host cell.
(d) the transformed cells will have the ability to resist ampicillin as well as produce β-galactoside.
Ans: (c)

• pBR322 is a commonly used cloning vector. When the gene for β-galactoside is inserted in the ampicillin resistance gene by using Pst I, the recombinant E.coli will lose ampicillin resistance due to insertional inactivation of the antibiotic resistance gene.
• The host (recombinant) cell will produce β-galactoside which is not a novel protein nor does it have dual ability.
• The transformed cells cannot resist ampicillin as they have lost ampicillin resistance.
• A recombinant E. coli is produced and the host cell will not undergo lysis due to insertion of β-galactoside gene.

Q5: During the process of gene amplification using PCR, very high temperature is not maintained in the beginning, then which of the following PCR will be affected first?        (NEET 2021)
(a) Denaturation
(b) Ligation
(c) Annealing
(d) Extension
Ans: (a)

• Option (d) is correct. Denaturation is first step of PCR that involves seperation of double-stranded DNA. The DNA is subjected to heating at high temperature (95^∘C). This leads to breaking of hydrogen bonds between nucleotides and formation of single-stranded DNA. Thus, if high temperature is not maintained, denaturation will be affected.
• Ligation of DNA fragments is performed with the help of an enzyme called DNA ligase.
• Annealing is performed at 50^∘-60^∘C which is the second step that can get affected.
• Addition of nucleotides to the primer, synthesizing a new DNA strand using only the template sequences with the help of enzyme DNA polymerase is called primer extension/polymerisation.

Q7: A specific recognition sequence identified by endonucleases to make cuts at specific positions within the DNA is:        (NEET 2021)
(a) Palindromic Nucleotide sequences
(b) Poly(A) tail sequences
(c) Degenerate primer sequence
(d) Okazaki sequences
Ans: (a)

• Each restriction endonuclease recognizes a specific palondromic nucleotide sequence in the DNA. Once it finds its specific recognition sequence it bind to DNA and cuts each of the two strands of DNA.
• During post transcriptional modification in eukaryotes, poly(A) tail (200-300 adenylate residues) are added at 3' end of hnRNA.
• During DNA replication Okazaki fragments are synthesized discontinuously and joined by DNA ligase.
• A PCR primer sequence is termed degenerate if some of its position have several possible bases.

2020

Q1: In-gel electrophoresis, separated DNA fragments can be visualized with the help of:        (NEET 2020)
(a) acetocarmine in UV radiation
(b) ethidium bromide in infrared radiation
(c) acetocarmine in bright blue light
(d) ethidium bromide in UV radiation
Ans: (d)
The separated DNA fragments can be visualised only after staining the DNA with Ethidium bromide followed by exposure to UV radiation.

Q2: Bt cotton variety that was developed by the introduction of toxin gene of Bacillus thuringiensis (Bt) is resistant to        (NEET 2020)
(a) Insect predators
(b) Insect pests
(c) Fungal diseases
(d) Plant nematodes
Ans: (b)
Bt cotton is resistant to cotton bollworn (Insect pest). cry I Ac and cry II Ab genes have been introduced in cotton to protect it from cotton bollworm. This makes Bt cotton as biopesticide.

Q3: Identify the wrong statement with regard to restriction enzymes.          (NEET 2020)
(a) They are useful in genetic engineering.
(b) Sticky ends can be joined by using DNA ligases.
(c) Each restriction enzyme functions by inspecting the length of a DNA sequence.
(d) They cut the strand of DNA at palindromic sites.
Ans: (b)
Restriction endonucleases make cuts at specific positions within the DNA. They function by inspecting the length of a DNA sequence. Restriction endonuclease binds to the DNA and cut the two strands of double helix at specific points in their sugarphosphate backbones. They are used in genetic engineering to form recombinant molecules of DNA. DNA ligases join the DNA fragments. 

Q4: The specific palindromic sequence which is recognized by EcoRI is:          (NEET 2020)
(a) 5’- CTTAAG -3’, 3’GAATTC - 5’
(b) 5’- GGATCC - 3’, 3’- CCTAGG - 5’
(c) 5’- GAATTC - 3’, 3’ -CTTAAG - 5’
(d) 5’ - GGAACC - 3’, 3’ - CCTTGG - 5’
Ans: (c)
The specific palindromic sequence which is recognised by EcoRI is
5’ - GAATTC - 3’
3’ - CTTAAG - 5’

Q5: The sequence that controls the copy number of the linked DNA in the vector, is termed        (NEET 2020)
(a) Palindromic sequence
(b) Recognition site
(c) Selectable marker
(d) Ori site
Ans: (d)
Ori sequence is responsible for controlling the copy number of the linked DNA in the vector. Ori i.e. origin of replication is responsible for initiation of replication.

Q6: Match the organism with its use in biotechnology.        (NEET 2020)

Select the correct option from the following

Ans: (d)
Bacillus thuringiensis is a source of Cry- proteins. Thermus aquaticus is a source of thermostable DNA polymerase (Taq polymerase) used in PCR. Agrobacterium tumefaciens is a cloning vector. The construction of 1st recombinant DNA molecule was performed using native plasmid of Salmonella typhimurium.

Q7: Choose the correct pair from the following        (NEET 2020)
(a) Nucleases - Separate the two strands of DNA
(b) Exonucleases - Make cuts at specified positions within DNA
(c) Ligases - Join the two DNA molecules
(d) Polymerases - Break the DNA into fragments
Ans: (c)
Ligases join the two DNA molecules. DNA ligase is an enzyme which can connect two strands of DNAtogether by forming a bond between the phosphate group of one strand and the deoxyribose group on another. It is used in cells to join together the Okazaki fragments which are formed on the lagging strand during DNA replication.

2019

Q1: The following statements describe the characteristics of the enzyme restriction endonuclease. Identify the incorrect statement.        (NEET 2019)
(a) The enzyme recognises a specific palindromic nucleotide sequence in the DNA.
(b) The enzyme cuts DNA molecule at an identified position within the DNA.
(c) The enzyme binds DNA at specific sites and cuts only one of the two strands.
(d) The enzyme cuts the sugar-phosphate backbone at specific sites on each strand.
Ans: (c)
Enzyme binds DNA at specific sitcs and cut both the strands by breaking phosphodiester linkage.

Q 20: DNA precipitation out of a mixture of biomolecules can be achieved by treatment with        (NEET 2019)
(a) Chilled chloroform
(b) Isopropanol
(c) Chilled ethanol
(d) Methanol at room temperature
Ans: (c)
Chilled ethanol is used for DNA precipitation out of a mixture of biomolecules. Process is called spooling.

2018

Q1: The correct order of steps in Polymerase Chain Reaction (PCR) is        (NEET 2018)
(a) Extension, denaturation, annealing
(b) Annealing, extension, denaturation
(c) Denaturation, extension, annealing
(d) Denaturation, annealing, extension
Ans: (d)
Each cycle of PCR has three steps :
(1) Denaturation,
(2) Primer annealing,
(3) Extension of primers.

2017

Q1:  The DNA fragments separated on an agarose gel can be visualised after staining with        (NEET 2017)
(a) Acetocarmine
(b) Aniline blue
(c) Ethidium bromide
(d) Bromophenol blue
Ans: (c)
Ethidium bromide (Et Br) is used to stain the DNA fragments and will appear as orange coloured bands when kept under UV light.

Q2: DNA fragments are        (NEET 2017)
(a) Negatively charged
(b) Neutral
(c) Either positively or depending on their size
(d) Positively charged
Ans: (a)
DNA fragments are negatively charged because of presence of phosphate group.

Q3: What is the criterion for DNA fragments movement on agarose gel during gel electrophoresis?        (NEET 2017)
(a) The smaller the fragment size, the farther it moves.
(b) Positively charged fragments move to the farther end.
(c) Negatively charged fragments do not move.
(d) The larger the fragment size, the farther it moves.
Ans: (a)
DNA fragments during gel electrophoresis, separate (resolve) according to their size due to sieving effect provided by agarose gel.

Q4: A gene whose expression helps to identify transformed cell is known as       (NEET 2017) 
(a) Vector
(b) Plasmid
(c) Structural gene
(d) Selectable marker
Ans: (d)
Selectable markers in recombinant DNA technology, helps in identification and elimination of non-transformants and selectively permits the growth of the transformants.

Q5: The process of separation mid purification of expressed protein before marketing is called        (NEET 2017)
(a) Downstream processing
(b) Bioprocessing
(c) Postproduction processing
(d) Upstream processing
Ans: (a)
The various stages of processing that occur after the completion of fermentation or biosynthetic stage which include separation and purification of product called downstream processing.

2016

Q1: Stirred-tank bioreactors have been designed for        (NEET 2016 Phase 2)
(a) Purification of product
(b) Addition of preservatives to the product
(c) Availability of oxygen throughout the process
(d) Ensuring anaerobic conditions in the culture vessel
Ans: (c)
A stirred-tank reactor is usually cylindrical or with a curved base to facilitate the mixing of the reactor contents. The stirrer facilitates, even mixing and oxygen availability throughout the biorcactor.

Q2: A foreign DNA and plasmid cut by the same restriction endonuclease can be joined to form a recombinant plasmid using        (NEET 2016)
(a) EcoRl
(b) Taq polymerase
(c) Polymerase III
(d) Ligase
Ans: (d)
Ligase is a class of enzymes that catalyse the formation of covalent bonds using the energy released by the cleavage of ATP. Ligases arc important in the synthesis and repair of many biological molecules, including DNA ligase and used in genetic engineering to insert foreign DNA into cloning vectors.

Q3: Which of the following is not a component of downstream processing?        (NEET 2016)
(a) Separation
(b) Purification
(c) Preservation
(d) Expression
Ans: (d)
After the formation of the product in bioreactor, it undergoes some processes before a finished product to be ready for marketing. Downstream processing includes separation and purification process. The product obtained is subjected to quality' control, testing and kept in suitable preservatives.

Q4: Which of the following restriction enzymes produces blunt ends?        (NEET 2016)
(a) Sal I
(b) Eco RV
(c) Xho I
(d) Hind III
Ans: (b)
EcoRV is a type II restriction endonuclease isolated from certain strains of E.coli. It creates blunt ends. It recognises the palindromic sequence of 6 bases. Sal I, Xho I and Hind lll restriction enzymes produce sticky ends.

Q5: Which of the following is not a feature of the plasmids?        (NEET 2016 Phase 1)
(a) Transferable
(b) Single-stranded
(c) Independent replication
(d) Circular structure

Ans: b
Plasmid has an extra chromosomal, double stranded circular DNA.

Q6: Which of the following is a restriction endonuclease?        (NEET 2016 Phase 1)
(a) DNase I
(b) RNasc
(c) Hind ll 
(d) Protease
Ans: (c)
A restriction enzyme or restriction endonuclease is an enzyme that cuts DNA at or near specific recognition nucleotide sequences known as restriction sites. Hind II among these is a type of restriction endonuclease.

Q7: Which of the following is not required for any of the techniques of DNA fingerprinting available at present?        (NEET 2016 Phase 1)
(a) Restriction enzymes
(b) DNA-DNA hybridisation
(c) Polymerase chain reaction
(d) Zinc finger analysis
Ans: (d)
Any small, functional, freely folded domain in which coordination of one or more zinc ions is required to stabilise its structure is known as zinc finger. The z.inc finger domains are widely dispersed in eukaryotic genomes and are actively involved in sequence specific binding to DNA/RNA and contribute in protein-protein recognitions.

Q8: The Taq polymerase enzyme is obtained from        (NEET 2016 Phase 1)
(a) Bacillus subtilis
(b) Pseudomonas putida
(c) Thermus aquaticus
(d) Thiobacillus ferroxidans
Ans: c()
The Taq polymerase enzyme is obtained from Thermus aquaticus which lives in hot springs.

2015

Q1: The cutting of DNA at specific locations became possible with the discovery of       (NEET 2015 / AIPMT 2015 )
(a) Probes
(b) Selectable markers
(c) Ligases
(d) Restriction enzymes
Ans: (d)
Restriction enzymes are used to cut DNA at specific locations

Q2:  The DNA molecule to which the gene of interest is integrated for cloning is called:        (NEET 2015 / AIPMT 2015 )
(a) Vector
(b) Template
(c) Carrier
(d) Transformer
Ans: (a)
Vector is a DNA molecule that carries a foreign DNA segment and replicates inside a host cell. The vector DNA and foreign DNA carrying gene of interest are cut by the same restriction endonuclease enzyme to produce complementary sticky ends. With the help of DNA ligase enzyme, the complementary sticky ends of the two DNAs are joined to produce a recombinant DNA (rDNA), which is then introduced into the host cell.

2014

Q1: An analysis of chromosomal DNA using the Southern hybridization technique does not use:        (NEET 2014 / AIPMT 2014 )
(a) Electrophoresis
(b) Blotting
(c) Autoradiography
(d) PCR
Ans: (d)
PCR is used only for amplification of DNA. It is not directly involved in Southern hybridisation technique.

Q2: Commonly used vectors for human genome sequencing are :        (NEET 2014 / AIPMT 2014 )
(a) BAC and YAC
(b) T/A Cloning Vectors
(c) T− DNA
(d) Expression Vectors
Ans: (a)
Bacterial artificial chromosome (BAC) vectors are based on natural, extra-chromosomal plasmid of E. coli. BAC vector contains genes for replication and maintenance of the F-factor, a selectable marker and cloning site. These vectors can accommodate upto 300-350 kb of foreign DNA and are also being used in genome sequencing project. Yeast artificial chromosome (YAC) vectors are used to clone DNA fragments of more than 1Mb in size. Therefore, they have been exploited extensively in mapping the large genomes, e.g., in the Human Genome Project. These vectors contain the telomeric sequence, the centromere and the autonomously replicating sequence from yeast chromosomes.

Q 45: Which vector can clone only a small fragment of DNA?        (NEET 2014 / AIPMT 2014 )
(a) Bacterial artificial chromosome
(b) Yeast artificial chromosome
(c) Plasmid
(d) Cosmid
Ans: (c)
Plasmids are small extranuclear circular DNAs that carry extrachromosomal genes in bacteria and some fungi. They replicate independently. The best-known vectors which are also available commercially are pBR322 and pUC-18.