Biology

DNA and Genetics

985 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 structure of dna and rna nucleic acids and polynucleotides nucleic acids and protein synthesis molecular biology biology

The enzyme which helps to cut one strand of DNA duplex to release tension of coiling of two strands is

  1. DNA ligase

  2. DNA polymerase I

  3. Topoisomerase

  4. Helicase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Topoisomerases are enzymes that manage DNA supercoiling by cutting one or both strands of the DNA backbone to relieve torsional strain.

Multiple choice structure of dna and rna nucleic acids and polynucleotides nucleic acids and protein synthesis molecular biology biology

Okazaki segments develop in

  1. Newly synthesised leading strand

  2. Newly synthesised lagging strand

  3. Master strand

  4. Template strands of DNA
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

During DNA replication, the lagging strand is synthesized discontinuously in short segments known as Okazaki fragments because DNA polymerase can only synthesize in the 5 prime to 3 prime direction. The leading strand, by contrast, is synthesized continuously.

Multiple choice zoology global environmental change causes of greenhouse effect global warming adaptation in animals

Ultra-violet light causes

  1. Formation of pyrimidines dimers

  2. Sticky metaphases

  3. Photodynamic action

  4. Destruction of hydrogen bonds between complementary DNA strands
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The Ultra-violet radiations are the potent mutagens as they are capable of distorting the structure of the DNA. The UV radiations cause the adjacent pyrimidines residues (thymine and cytosine) to form hydrogen bonds with each other rather than the corresponding purine residues. Generally, the thymine dimers are seen as immediate effects of the UV radiations. Due to this type of mutation, the errors in replication of DNA are frequent to observe. The breaking of hydrogen bonds between the two complementary DNA strands occurs due to increase in temperature. This is not considered as a mutation because when normal conditions arrive the hydrogen bonds can be formed again.

Hence, the correct answer is 'Formation of pyrimidines dimers'.

Multiple choice biology classification of plants monera five kingdoms of living organisms biodiversity and need of classification

On what basis plasmids can be separated?

  1. Their size

  2. Their charge

  3. Their A-T:G-C compositiion

  4. Both (A) and (B)

  5. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Plasmid DNA can be analysed using agarose gel electrophoresis. When sample of DNA is loaded, onto the agarose gel and electric field is applied, it results in separation of DNA molecules according to their size and shape. On agarose gel, small molecules of DNA are able to pass easily in the electric field. DNA possesses strong negative charge which helps in its movement towards positive electrode in the electrophoresis apparatus. Along with size and shape of DNA molecule, electrophoresis buffer type also determines the rate of migration of DNA molecule.

Multiple choice botany the world of microbes bacteria - introduction, shape and structure bacteria: types and structure bacteria; benefits and harmful effects non cellular organism : virus world of virus

DNA of E.coli  

  1. ds circular

  2. ss circular

  3. ds linear

  4. ss linear
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  E. coli , a gram negative rod shaped bacteria has since the time of discovery have been commonly used for biological lab experiment and research. The simple cell structured E. coli has one circular chromosome and a ds circular DNA molecule with 4.6 million base pairs in length and 4288 protein coding genes.

Multiple choice botany bacteria bacteria - introduction, shape and structure bacteria: types and structure bacteria; benefits and harmful effects

Which one of the following is the basis of biological control of crown gall?

  1. Agro bacterium radiocasted strains contain a plasmid which directs the synthesis of bactenocin

  2. The Ti(tumour inducing) plasmid in Agro bacterium tumefactions is integrated with host plant DNA and is transcribed into mRNA

  3. The cloning strategy leading to a composite(chimeric) plasmid harbouring two or more genes that code for distinct bacteriocins against phytopathogenic bacteria

  4. Agrobacterium radiobacter plasmid interferes with the production of auxin by a tumefaction
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Agrobacterium radiobacter strain K84 is used for the biological control of crown gall disease. It produces a bacteriocin called agrocin 84, which inhibits the growth of pathogenic Agrobacterium tumefaciens.

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.