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Biotechnology : Principles and Processes

Multiple Choice Questions

21.

A bacterium divides after every 35 min, if a culture containing 105 cells per mL is grown, then cell concentration per mL after 175 mins will be

• 175$×$105

• 125$×$105

• 48$×$105

• 32$×$105

D.

32$×$105

As we know, the bacterium divides after every 35 minutes through simple mitotic division. Therefore, number of divisions are $\frac{175}{35}$$=5$.

Since, one bacterium on division produces 2 cells, so, cell concentration after 175 minutes will be

= 10$×$ (2)5

= 32$×$105

22.

Molecular scissors, which cut DNA at specific site is

• pectinase

• polymerase

• restriction endonuclease

• ligase

C.

restriction endonuclease

A restriction enzyme or restriction endonuclease is an enzyme that cleaves DNA into fragments at or near specific recognition sites within the molecule known as restriction sites.

23.

What is true about Bt toxin

• The inactive protoxin gets converted into active form in the insect gut

• Bt protein exists as active toxin in the bacillus

• The activated toxin enters the ovaries of the pets to sterilise it and thus prevent its multiplication

• The activated toxin enters the ovaries of the pets to sterilise it and thus prevent its multiplication

A.

The inactive protoxin gets converted into active form in the insect gut

Bacillus thuringiensis toxin is an inactive protoxin, which gets converted into an active form in the insect gut. It works as an insecticide.

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24.

Assertion : Restriction enzymes cut the strand of DNA to produce sticky ends.

Reason : Stickiness of the ends facilitates the action of the enzyme DNA polymerase.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

C.

If assertion is true but reason is false

A restriction enzyme or restriction endonuclease is an enzyme that cleaves DNA into fragments at or near specific recognition sites within the molecule known as restriction sites. Once restriction enzyme finds a recognition sequence, it binds and cut each of the two strands of the double helix at specific point leaving single stranded portions at the ends. This resulta in the overhanging stretches known as sticky ends.

These are so named because they form hydrogen bonds with their complementary counter parts ,ie, they can join similar complementary ends of DNA fragment from some other source with the help of DNA ligase. This stickiness of the ends facilitates the action of the enzyme DNA ligase, not DNA polymerase.

25.

The genetically - modified (GM) brinjal in India has been developed for

• insect - resistance

• enhancing self- life

• enhancing mineral content

• enhancing mineral content

A.

insect - resistance

The genetically modified brinjal or Bt brinjal has the same Cry - LAC gene from Bacillus thuringiensis as cotton. The gene from Bacillus thuringiensis as cotton. The gene is supposed to make the plant tolerant to the shoot and fruit borer insect, which attacks it throughout its life cycle.

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26.

Recombinant DNA technology involves several steps in which initial step is of isolation of the DNA. Which enzymes are used in the process for the breakdown of fungal cell, plant cell and bacterial cell respectively?

• Lysozyme, lipases, trypsin

• Chitinase, cellulase, lysozyme

• Chitinase, cellulase, trypsin

• Trypsin, lipases, cellulase

B.

Chitinase, cellulase, lysozyme

Process of RDT or Recombinant DNA Technology involves isolation of DNA of a desired DNA fragment. The DNA should be in pure form, free form other macro- molecules.

The bacterial cell or plant or an animal tissue is treated with enzyme lysozyme or cellulase or chitinase (fungal) enzyme respectively in order to break the cell to release DNA. RNA can be removed by treated the cell with ribonuclease and proteins can be removed by treatment with protease.

27.

What is a plasmid?

• Bacterial, linear, dsDNA

• Extrachromosomal linear RNA

• Extrachromosomal circular dsDNA

• Autonomously replicating circular RNA

C.

Extrachromosomal circular dsDNA

Plasmid is a structure present in bacterial cells that consists of DNA whichis self- replicating. It is an extra- chromosomal circular double stranded DNA that provides genetic information for various cell activities. For eg, resistance to antibiotic drugs. They are widely used as vectors to produce recombinant DNA for gene cloning.

28.

Restriction endonucleases are enzymes which

• make cuts at specific positions within the DNA molecule

• recognize a specific nucleotide sequence for binding of DNA ligase

• restrict the action of the enzyme DNA polymerase

• restrict the action of the enzyme DNA polymerase

A.

make cuts at specific positions within the DNA molecule

Restriction endonucleases recognise a specific DNA base sequence (recognition sequence of the recognition site, restriction sequence or restriction site) and cleave both the strands of DNA at or near the site. The enzyme cuts are DNA, generating restriction fragments wit overhanging ends or blunt ends.

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29.

Stirred -tank bioreactors have been designed for

• the addition of preservatives of the product

• purification of the product

• ensuring anaerobic conditions in the culture vessel

• ensuring anaerobic conditions in the culture vessel

D.

ensuring anaerobic conditions in the culture vessel

The most common type of aerobic bioreactor in use today is the stirred tank- reactor, which may feature a specific internal configuration designed to provide a specific circulation pattern. The stirred tank bioreactor have been designed for the availability of oxygen throughout the processes.

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30.

Science of engineering and technology applied to life sciences is

• Biotechnology

• Genetic engineering

• Pathology

• Biological science

A.

Biotechnology

Biotechnology includes the use of living organisms or substances obtained from them, in industrial processes. It is an integrated use of different disciplines like microbiology, biochemistry and chemical engineering.