Biology

DNA and Genetics

1,095 Questions

DNA and genetics questions explore molecular biology, DNA replication, and genetic engineering techniques. These topics are essential for various competitive exams requiring a strong foundation in life sciences. Practice these questions to understand complex biological processes thoroughly.

DNA replication mechanismsGenetic engineering techniquesGene editing toolsPolymerase chain reactionDNA sequencing methods

DNA and Genetics Questions

Multiple choice botany the living world archaebacteria the three domains of life classification of microbes

Choose the correct answers from the alternatives given.
During bacterial conjugation there is

  1. a partial but mutual exchange of genetic material between the conjugants

  2. only a partial transfer of genetic material from one conjugant to the other

  3. a mutual and complete exchange of genetic material between two conjugants

  4. a complete transfer of genetic material from one conjugant to the other
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Bacterial conjugation is the transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells. So the correct option is 'a complete transfer of genetic material from one conjugant to the other'.
Multiple choice biology cell-the basic unit of life nucleus organelles in cell membranous and non-membranous organells

The nucleus possessed the ability to control phenotype was first determined by

  1. Experiments with radiolabelled phages

  2. Experiments with bacteria that identified DNA polymerase

  3. Transformation experiments with Streptococcus pneumoniae

  4. Identification of restriction endonucleases

  5. Grafting experiments with Acetabularia
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Acetabularia consists of a rootlike holdfast, a long, cylindrical stalk; and a cuplike cap. The nucleus is present in the holdfast. Acetabularia exhibits regeneration of the cap after any injury. A. mediterranea has a smooth cap and A. crenulata, has a cap with fingerlike projections. Danish biologist J. Hämmerling and Belgian biologist J. Brachet performed grafting experiment on above mentioned species and showed that type of caps that regenerated were determined by the type of the donor species of the holdfasts, not by those donating the stalks. It was concluded, that nucleus in the holdfast of Acetabularia controls the shape of the caps. The correct answer is E.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Enzyme' Taq polymerase' used in PCR, has been isolated from bacterium _________________.

  1. Agrobacterium tumefaciens

  2. Thermus aquaticus

  3. Streptomyces albus

  4. Escherichia coli
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The final step of PCR is the extension, wherein Taq DNA polymerase is isolated from a thermophilic bacterium Thermus aquaticus.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Which of the following statements are correct for the enzyme Taq polymerase?


(i) It remains active during the high temperature-induced denaturation of dsDNA.

(ii) It requires primers for carrying out the process of polymerisation.
(iii) It synthesizes the RNA region between the primers, using $dNTPs$ and $Mg^{2+}$ _______________.

  1. (i) and (ii)

  2. (ii) and (iii)

  3. (i), (ii) and (iii)

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The final step of PCR is the extension, wherein Taq DNA polymerase (isolated from a thermophilic bacterium Thermus aquaticus) synthesizes the DNA region between the primers, using dNTPs (deoxynucleoside triphosphates) and $Mg^{2+}$. The primers are extended towards each other so that the DNA segment lying between the two primers is copied. The optimum temperature for this polymerisation step is $72^o$$C$. Taq polymerase remains active during high temperature-induced denaturation of double-stranded DNA.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Primers are

  1. Chemically synthesised oligonucleotides that are complementary to the regions of DNA

  2. Chemically synthesised oligonucleotides that are not complementary to the regions of DNA

  3. Chemically synthesised, autonomously replicating circular DNA molecules

  4. Specific sequences present on recombinant DNA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Primers are small, chemically synthesised oligonucleotides that are complementary to the sequences, present at 3' end of the template DNA. They hybridise to the target DNA region, one to each strand of the double helix. These primers are oriented with their ends facing each other allowing synthesis of the DNA towards one another.
So, the correct answer is 'Chemically synthesised oligonucleotides that are complementary to the regions of DNA'.
Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Given table gives an account of differences between PCR and gene cloning. Which of the, following points shows the incorrect difference?

  Parameter PCR Gene cloning
1 Efficient More Less
2 Apparatus Requirement DNA Restriction enzyme, ligase, vector, bacterial cell
3 Manipulation In vitro In vitro and in vivo
4 Cost More Less
5 Automation Yes No
6 Error probability Less More
7 Time for a typical experiment 2-4 days 4 hours
8 Application More Less


  1. 1 and 3

  2. 4 and 6

  3. 4 and 7

  4. 4, 7 and 8
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The cost of gene cloning is far more than PCR because gene cloning requires many intricate steps. PCR takes less than 4 hours while gene cloning can take days.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

In a polymerase chain reaction, temperature required for the steps (i) Denaturation,(ii) Annealing, and (iii) Extension are respectively.

  1. (i) $94^o$$C$ (ii) $40^o$$C$ (iii) $72^o$$C$
  2. (i) $40^o$$C$ (ii) $72^o$$C$ (iii) $94^o$$C$
  3. (i) $94^o$$C$ (ii) $72^o$$C$ (iii) $40^o$$C$
  4. (i) $72^o$$C$ (ii) $94^o$$C$ (iii) $40^o$$C$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • At the start of PCR, the DNA from which a segment is to be amplified, an excess of the two primer molecules, the four deoxynucleoside triphosphates and the DNA polymerase are mixed in the reaction mixture that has appropriate quantities of $Mg^{2+}$. 
  • The reaction mixture is first heated to a temperature between $90-$$98^oC$ (commonly $94^oC$) that ensures DNA denaturation. Every single strand of the target DNA then acts as a template for DNA synthesis. This is the denaturation step. The duration of this step in the first cycle of PCR is usually 2 min at  $94^oC$. 
  • The mixture is now cooled to a temperature (generally $40-60^oC$) that permits annealing of the primer to the complementary sequences in the DNA. This step is called annealing. The duration of the annealing step is usually 1 min.
  • The primers are extended towards each other so that the DNA segment lying between the two primers is copied, this is ensured by employing primers complementary to the 3': ends of the segment to be amplified. The duration of primer extension is usually 2 min at $72^oC$. 
Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

In addition to Taq polymerase enzyme which other thermostable DNA polymerases have been isolated to be used in polymerase chain Reaction (PCR)?

  1. Pfu polymerase isolated from Pyrococcus furiosus

  2. Tli polymerase (vent polymerase) isolated from Thermococcus litoralis

  3. Both (a) and (b)

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In addition to Tag DNA polymerase, Pfu polymerase and Tli polymerase have been isolated which are also thermostable. Pfu polymerase is isolated from Pyrococcus furiosus. Tli (vent) polymerase is isolated from Thermococcus litoralis.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Which one of the following is not a correct match?

  1. Tumor Inducing - Ti plasmid

  2. DNA probe - Identifies the desired DNA fragment

  3. PCR - DNA staining

  4. Agarose - Sea weeds
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

PCR is a method for DNA amplification, not DNA staining. DNA staining is typically performed using dyes like ethidium bromide or SYBR Green.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

The correct sequence of different steps of polymerase chain reaction is

  1. Annealing denaturation extension

  2. Denaturation extension annealing

  3. Denaturation annealing extension

  4. Extension denaturation annealing
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Polymerase chain reaction is a technique used to replicate a fragment of DNA so as to produce many copies of a particular DNA sequence. A single PCR amplification cycle involves three basic steps: denaturation, annealing and extension (polymerisation).
So, the correct answer is 'Denaturation annealing extension'.
Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Given figures represent the steps involved in polymerase chain reaction (PCR). Identify the steps A, B, C and D, and select the correct option.

A B C D
a Denaturation at 94-96 degree C Extension through Taq polymerase at 72 degree C Repetition of denaturation and annealing Annealing at 72 degree C
b Denaturation at 94-96 degree C Annealing at 40-60 degree C Extension through Taq polymerase at 72 degree C Repetition of denaturation and annealing
c Denaturation at 40-60 degree C Annealing at 72 degree C Extension through Taq polymerase at 94-96  degree C Repetition of denaturation and annealing
d Extension through Taq polymerase at 72 degree C Denaturation at 40 degree C Annealing at 72 degree C Repetition of denaturation and annealing

  1. a

  2. b

  3. c

  4. d
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Polymerase chain reaction involves the steps:

  • Denaturation
  • Annealing 
  • Extension
  • Amplification
So, the correct option is 'Option B ' .

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Study the following statements regarding recombinant DNA technology and select the incorrect ones

(i) Taq polymerase extends the primers using the nucleotides provided in the reaction
(ii) Antibiotic resistance genes are considered as desirable genes in recombinant DNA technology
(iii) DNA fragments are separated according to their charge only, in agarose gel electrophoresis
(iv) Transformation is a procedure through which a piece of DNA is integrated into the genome of a host bacterium
(v) To produce higher yields of the desired protein, host cells can be multiplied in a continuous culture
(vi) Downstream processing is one of the steps of polymerase chain reaction

  1. (i), (iii) and (vi)

  2. (i), (iii) and (v)

  3. (ii), (iii) and (v)

  4. (i), (iv) and (v)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Antibiotic resistance genes are selectable markers. Desirable genes are the ones which are introduced in the vector for getting desired protein product. In agarose gel electrophoresis, DNA fragments are separated according to their charge and size. After the formation of the product in a bioreactors, it undergoes through some processes before a finished product is ready for marketing. The processes include separation and purification of products which are collectively called as downstream processing.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Reaction of 1989 was

  1. Nicking by restriction endonucleases

  2. Polymerase chain reaction

  3. Reverse genetics

  4. Splicing
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In 1985 Norm Arnheim, also a member of the development team concluded his sabbatical at Cetus and assumed an academic position at USC. He began to investigate the use of PCR to amplify samples containing just a single copy of the target sequence. By 1989 his lab developed multiplex-PCR on single sperm to directly analyze the products of meiotic recombination.

So, the correct answer is 'Polymerase chain reaction.'

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

DNA taq polymerase enzyme is isolated from which bacteria?

  1. Agrobacterium

  2. Thermus aquaticus

  3. Bacillus thuringiensis

  4. E.coli
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

DNA polymerase enzyme was isolated from a thermophilc bacteria called Thermus aquaticus. This is an enzyme used frequently to make multiple copies of segment of DNA by a technique called polymerase chain reaction.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Thermal cycle is used in

  1. Radioactivation

  2. Chemical reaction

  3. Polymerase chain reaction

  4. Enzyme catalysed reactions
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A thermal cycler is an instrument used to perform PCR by precisely controlling the temperature changes required for denaturation, annealing, and extension.