NEET Biology Biotechnology Principles and Processes MCQs Set 10

Answer: (d) Hind II

Explanation:
1. Hind II was the first restriction endonuclease to be isolated; it always cuts at a specific point by recognising a particular sequence of six base pairs.
2. EcoRI was discovered later.
3. Adenosine deaminase is not a restriction enzyme and Taq polymerase is a thermostable DNA polymerase.

Teacher's Note:
1. Hind II is the first restriction enzyme and EcoRI the most famous one.
2. Restriction enzymes come from bacteria.

Answer: (d) as selectable markers

Explanation:
1. Antibiotic resistance genes such as ampR and tetR act as selectable markers in a vector.
2. Only transformed cells survive on a medium containing the antibiotic, which helps to detect recombinants.

Teacher's Note:
1. A selectable marker helps to identify and eliminate non-transformants.
2. Antibiotics here are used for selection, not to keep the medium sterile.

Answer: (b) (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)

Explanation:
1. A bioreactor is used for the production of large quantities of products, electrophoresis for separation of DNA fragments, PCR for amplification of nucleic acids and ELISA for detection of pathogens by antigen-antibody reaction.
2. So the matching is a-ii, b-i, c-iv, d-iii.

Teacher's Note:
1. Link every technique with its single main use.
2. ELISA works on antigen-antibody interaction.

Answer: (c) Electrophoresis

Explanation:
1. The negatively charged DNA fragments migrate through an agarose gel towards the anode under an electric field.
2. Smaller fragments move faster, so a mixture is separated by size.

Teacher's Note:
1. Electrophoresis separates, PCR amplifies and restriction digestion cuts.
2. Keep these three techniques distinct.

Answer: (c) Restriction enzyme digestions are performed by incubating purified DNA molecules with the restriction enzymes of optimum conditions.

Explanation:
1. Restriction digestion is carried out by incubating purified DNA with the restriction enzyme under optimum conditions.
2. Gel electrophoresis separates fragments instead of amplifying them, ligase (not polymerase) joins DNA and PCR amplifies a segment.

Teacher's Note:
1. Optimum temperature and buffer are needed for enzyme activity.
2. Cut DNA, then run it on a gel.

Answer: (c) (iv) (iii) (i) (ii)

Explanation:
1. Bacillus thuringiensis produces Cry proteins, Thermus aquaticus gives the thermostable Taq DNA polymerase, Agrobacterium tumefaciens supplies the Ti plasmid vector and Salmonella typhimurium plasmid was used to construct the first rDNA molecule.
2. The matching is a-iv, b-iii, c-i, d-ii.

Teacher's Note:
1. Taq polymerase is used in PCR as it survives denaturation at high temperature.
2. Cohen and Boyer made the first rDNA using a Salmonella plasmid.

Answer: (b) 5' - GAATTC - 3' 3' - CTTAAG - 5'

Explanation:
1. EcoRI recognises the palindromic sequence 5'-GAATTC-3', which reads GAATTC on the complementary strand 3'-CTTAAG-5'.
2. A palindrome reads the same in 5' to 3' direction on both strands.

Teacher's Note:
1. Palindromic sites read alike in the 5' to 3' direction on both strands.
2. EcoRI makes staggered cuts between G and A.

Answer: (b) (iv) (i) (ii) (iii)

Explanation:
1. Bt cotton is linked to Bacillus thuringiensis, adenosine deaminase deficiency is treated by gene therapy, RNAi is a cellular defence mechanism and PCR is used to detect HIV infection.
2. So the order is a-iv, b-i, c-ii, d-iii.

Teacher's Note:
1. PCR can detect low-titre pathogens early.
2. RNAi silences specific mRNA.

Answer: (a) Sticky ends can be joined by using DNA ligases.

Explanation:
1. Restriction enzymes recognise specific palindromic sequences and cut both strands; the sticky ends formed can be joined by DNA ligase.
2. They are not inspecting the length of a DNA sequence but its nucleotide sequence, so that statement is wrong.

Teacher's Note:
1. Enzymes inspect the sequence of the DNA, not its length.
2. They are the molecular scissors of genetic engineering.

Answer: (c) Ori site

Explanation:
1. The origin of replication (ori) is the sequence from which replication starts and which controls the copy number of the linked DNA in the vector.

Teacher's Note:
1. Ori decides how many copies of the plasmid are made inside the host.
2. A selectable marker only helps in selection.

Answer: (c) Ethidium bromide in UV radiation

Explanation:
1. DNA fragments separated on an agarose gel are stained with ethidium bromide and seen as orange-red bands under UV radiation.
2. Acetocarmine is a chromosome stain.

Teacher's Note:
1. Ethidium bromide plus UV light shows the DNA bands.
2. Purified fragments are then cut out of the gel (elution).

Answer: (b) Ligases :Join the two DNA molecules

Explanation:
1. Ligases join two DNA molecules.
2. Exonucleases remove nucleotides from the ends, polymerases synthesise DNA and endonucleases cut within the DNA.

Teacher's Note:
1. Do not confuse exonuclease (ends) with endonuclease (within the DNA).
2. Ligase is the molecular glue.

Answer: (b) a-iii, b-iv, c-i, d-ii

Explanation:
1. Restriction endonuclease cuts DNA at specific positions, restriction exonuclease removes nucleotides from the ends of DNA, DNA ligase joins fragments and Taq polymerase extends primers on a template.
2. The pairing is a-iii, b-iv, c-i, d-ii.

Teacher's Note:
1. Learn each enzyme with one action word: cut, trim, join, extend.
2. Endo means within, exo means outside.

Answer: (a) Ampicillin and Tetracycline

Explanation:
1. The vector pBR322 has two antibiotic resistance genes, ampR (ampicillin) and tetR (tetracycline), along with ori and the rop gene.

Teacher's Note:
1. pBR322 carries ampicillin and tetracycline resistance.
2. Insertional inactivation of one gene identifies recombinants.

Answer: (a) help in eliminating the non-transformants, so that the transformants can be regenerated

Explanation:
1. A selectable marker helps in eliminating non-transformants so that transformants can be selected and regenerated.
2. It does not choose the vector or mark a gene for isolation.

Teacher's Note:
1. Markers are used for selection of transformed cells.
2. Antibiotic resistance genes are the usual markers.

Answer: (c) Exonuclease

Explanation:
1. Exonuclease removes nucleotides from the ends of a DNA molecule, whereas endonuclease cuts within the DNA.
2. Ligase joins fragments and proteases act on proteins.

Teacher's Note:
1. Exo acts at the ends, endo acts inside.
2. Nucleases act on nucleic acids.

Answer: (d) Bioreactor

Explanation:
1. Large scale culture of microbes for industrial production of enzymes needs a bioreactor.
2. A BOD incubator, sludge digester and oven cannot give controlled large-scale growth.

Teacher's Note:
1. Bioreactors provide controlled temperature, pH and oxygen.
2. Stirred-tank and sparged-stirred types are common.

Answer: (c) Genetic code is nearly universal

Explanation:
1. The genetic code is nearly universal, so the same codon specifies the same amino acid in bacteria and humans.
2. This is why a human gene can be expressed in bacteria to make insulin.

Teacher's Note:
1. Universality of the code makes recombinant expression possible.
2. Degeneracy is a different property.

Answer: (b) The enzyme binds DNA at specific sites and cuts only one of the two strands.

Explanation:
1. A restriction endonuclease recognises a specific palindromic sequence and cuts the sugar-phosphate backbone on both strands at specific positions.
2. The statement that it cuts only one of the two strands is incorrect.

Teacher's Note:
1. Cutting both strands gives sticky or blunt ends.
2. A single-strand cut would make a nick only.

Answer: (a) Retrovirus

Explanation:
1. Retroviruses are used as vectors to introduce a DNA fragment into animal cells such as human lymphocytes, as in ADA gene therapy.
2. Ti plasmid works in plants and pBR322 and lambda phage are used in bacteria.

Teacher's Note:
1. Retroviral vectors integrate into the animal genome.
2. The Ti plasmid is used for dicot plants.

Answer: (a) Downstream processing

Explanation:
1. The process of separation and purification of the expressed protein before marketing is called downstream processing.
2. Upstream processing is the growth of the cells in the bioreactor.

Teacher's Note:
1. Downstream processing includes separation, purification and preservation.
2. It is followed by quality control tests.

Answer: (a) availability of oxygen throughout the process

Explanation:
1. Stirred-tank bioreactors are designed so that the contents are mixed well and oxygen is available throughout the culture process.
2. A sparger bubbles sterile air through the culture.

Teacher's Note:
1. Stirring provides even mixing and oxygen transfer.
2. Anaerobic culture does not need a sparger.

Answer: (b) Expression

Explanation:
1. Downstream processing consists of separation, purification, formulation and preservation of the product.
2. Expression of the gene happens before that, in the bioreactor.

Teacher's Note:
1. Expression is part of upstream work.
2. Quality control tests and clinical trials follow downstream processing.

Answer: (d) Single - stranded

Explanation:
1. Plasmids are extrachromosomal, double-stranded, circular DNA molecules in bacteria that replicate independently and can be transferred between cells.
2. They are not single-stranded.

Teacher's Note:
1. Plasmids are double-stranded and circular.
2. They are the commonest cloning vectors.

Answer: (d) Insertional inactivation of beta-galactosidase in recombinant bacteria

Explanation:
1. In pUC-type vectors with lacZ, the insertion of foreign DNA inactivates the gene for the enzyme beta-galactosidase.
2. Recombinant colonies cannot convert the chromogenic substrate, so they stay white, whereas non-recombinants give blue colonies.

Teacher's Note:
1. Insertional inactivation of beta-galactosidase gives white recombinants.
2. Blue colour indicates no insert.

Answer: (d) Transformation of plants cells

Explanation:
1. A biolistic or gene gun fires DNA-coated gold or tungsten micro-particles into cells at high velocity.
2. It is mainly suitable for transformation of plant cells.

Teacher's Note:
1. Gene gun is the direct gene transfer method for plants.
2. It is also known as particle bombardment.

Answer: (b) ampR, tetR-antibiotic resistance genes

Explanation:
1. In pBR322, ampR and tetR are antibiotic resistance genes, used as selectable markers.
2. Hind III and EcoRI are restriction sites, ori is the origin of replication and rop codes for a protein controlling the plasmid copy number.

Teacher's Note:
1. Ampicillin and tetracycline resistance genes are marked as ampR and tetR.
2. Restriction sites appear as enzyme names.

Answer: (c) (B) and (D) only

Explanation:
1. Plasmids and bacteriophages can carry foreign DNA into a host cell and are used as vectors.
2. A whole bacterium or Plasmodium cannot serve as a vector in this sense.

Teacher's Note:
1. Common vectors are plasmids, bacteriophages and the Ti plasmid.
2. Retroviruses are used for animal cells.