NEET Biology Biotechnology Principles and Processes MCQs Set 05

Answer: (c) Smith

Explanation:
1. The first restriction endonuclease to be isolated and characterised was HindII, isolated by Smith from the bacterium Haemophilus influenzae.
2. So the answer is Smith.

Teacher's Note:
1. Temin and Baltimore are linked with reverse transcriptase, and Sanger with DNA sequencing.
2. Paul Berg made the first recombinant DNA molecule.

Answer: (c) Ti plasmids of Agrobacterium

Explanation:
1. Agrobacterium tumefaciens infects dicot plants and transfers a piece of its DNA (T-DNA) to the plant cell.
2. Its tumour-inducing (Ti) plasmid is disarmed and used to deliver desired genes into plant cells.

Teacher's Note:
1. The T-DNA of the Ti plasmid integrates into the plant genome.
2. Retroviruses are used as vectors for animal cells.

Answer: (a) Ti plasmid

Explanation:
1. The tumour-inducing plasmid of Agrobacterium tumefaciens is called the Ti plasmid.
2. The Ri plasmid belongs to Agrobacterium rhizogenes, and pBR322 is an artificial E. coli vector.

Teacher's Note:
1. Ti stands for tumour inducing.
2. The T-DNA segment of the Ti plasmid causes the tumour.

Answer: (a) Plasmids are widely used in gene transfer

Explanation:
1. Plasmids are small circular extrachromosomal DNA molecules of bacteria that replicate independently.
2. They carry non-essential genes such as antibiotic resistance and are widely used as vectors in gene transfer.

Teacher's Note:
1. Plasmids are not part of the chromosome and are not needed for vital activities.
2. They are found in bacteria and some yeasts, not in viruses.

Answer: (a) Restriction endonuclease

Explanation:
1. Cutting DNA at specific sites with restriction endonucleases made it possible to cut and recombine DNA fragments.
2. Ligase then joins them, but the key discovery that began DNA manipulation was the restriction endonuclease.

Teacher's Note:
1. Restriction enzymes are called molecular scissors.
2. Ligase is the molecular glue.

Answer: (a) Are endonucleases which cleave DNA at specific sites

Explanation:
1. Restriction enzymes are endonucleases that recognise a specific palindromic sequence and cut the DNA there.
2. They only cut; joining is done by ligase, and they make no complementary strands.

Teacher's Note:
1. Cutting is by restriction enzymes and joining is by ligase.
2. Complementary strands are made by polymerases.

Answer: (d) All of the above

Explanation:
1. Direct (vectorless) gene transfer puts DNA into cells without a vector.
2. Microinjection, electroporation and the particle (gene) gun are all vectorless methods.

Teacher's Note:
1. In microinjection DNA is injected directly into the nucleus.
2. The gene gun fires DNA-coated gold or tungsten particles.

Answer: (c) Forensic investigation

Explanation:
1. PCR amplifies tiny amounts of DNA many thousand times.
2. This makes it useful in forensic investigation, where a very small DNA sample from a crime scene must be amplified for fingerprinting.
3. The other options are unrelated to PCR.

Teacher's Note:
1. PCR is also used in early diagnosis of diseases and in gene cloning.
2. It needs a template, primers, nucleotides and Taq polymerase.

Answer: (b) Protecting the bacterial DNA against foreign DNA

Explanation:
1. Bacteria make restriction enzymes to cut foreign DNA such as that of bacteriophages, which restricts phage growth.
2. Its use in genetic engineering is a human application, not its natural function.

Teacher's Note:
1. That is how the name restriction came about.
2. The bacterium protects its own DNA by methylating it.

Answer: (c) Making transient pores in the cell membrane to introduce gene constructs

Explanation:
1. In electroporation a short electric pulse is applied to cells.
2. This makes temporary pores in the cell membrane through which DNA enters.

Teacher's Note:
1. The pores close again after the pulse.
2. It is a vectorless method of transformation.

Answer: (d) Protect its DNA from its own restriction enzyme

Explanation:
1. Methylation of its recognition sequences stops the bacterium's own restriction enzymes from cutting its DNA.
2. Foreign unmethylated DNA is cut.

Teacher's Note:
1. This restriction-modification system is a bacterial defence.
2. The modification enzyme is a methylase.

Answer: (a) Ti plasmid

Explanation:
1. The tumour-inducing plasmid of Agrobacterium tumefaciens is the Ti plasmid.
2. The Shine-Dalgarno sequence is a ribosome-binding site on bacterial mRNA.

Teacher's Note:
1. Ti plasmids are made harmless before being used as vectors.
2. The tumour genes are removed from the T-DNA.

Answer: (c) Ligase

Explanation:
1. DNA ligase seals the nicks in the sugar-phosphate backbone and joins DNA fragments.
2. Endonucleases cut DNA, and DNA polymerase adds nucleotides on a template.

Teacher's Note:
1. Ligase is the molecular glue.
2. Both the vector and the insert must be cut with the same enzyme so they can be joined.

Answer: (b) Retrovirus

Explanation:
1. Retroviruses are used as vectors for transferring genes into animal (higher organism) cells.
2. Baculovirus infects insects and is not the usual vector for higher organisms. Salmonella is a bacterium and Neurospora a fungus.

Teacher's Note:
1. Disarmed retroviruses are used in gene therapy.
2. For plants, Ti plasmid is used.

Answer: (a) Denaturation, annealing, synthesis

Explanation:
1. Denaturation at about 94 degrees C separates the two strands.
2. Annealing at about 54 degrees C lets the primers bind.
3. Extension (synthesis) at about 72 degrees C lets Taq polymerase make new strands.

Teacher's Note:
1. Taq polymerase is heat stable, so it survives the denaturation step.
2. The cycle is repeated many times for amplification.

Answer: (a) Agrobacterium tumefaciens

Explanation:
1. The Ti plasmid comes from the soil bacterium Agrobacterium tumefaciens.
2. Thermus aquaticus is the source of Taq polymerase.

Teacher's Note:
1. Aedes aegypti is a mosquito.
2. Pyrococcus furiosus is another heat-loving source of polymerase.

Answer: (c) Restriction endonucleases

Explanation:
1. Restriction endonucleases cut DNA at specific recognition sites, so they are called molecular scissors.
2. Ligases are the molecular glue.

Teacher's Note:
1. Polymerases make new strands.
2. Each restriction enzyme has its own recognition site.

Answer: (c) 1972

Explanation:
1. Stanley Cohen and Herbert Boyer made the first recombinant DNA in 1972 by linking an antibiotic resistance gene to a plasmid of Salmonella typhimurium.

Teacher's Note:
1. This work marks the start of recombinant DNA technology.
2. They used restriction enzymes and ligase.

Answer: (c) Biotechnology

Explanation:
1. This is the EFB definition of biotechnology.

Teacher's Note:
1. Biotechnology combines biology with engineering to make products.
2. Bioinformatics deals with biological data.

Answer: (b) DNA ligase

Explanation:
1. Sticky ends of the vector and insert base-pair with each other.
2. This brings the fragments together, which makes the work of DNA ligase easier.

Teacher's Note:
1. Sticky ends are single-stranded complementary overhangs.
2. EcoRI makes sticky ends.

Answer: (b) Gel electrophoresis

Explanation:
1. Agarose gel electrophoresis separates DNA fragments by size.
2. Comparing digested lanes with undigested DNA shows how far the digestion has gone.

Teacher's Note:
1. Smaller fragments move farther through the gel.
2. DNA is seen under UV after ethidium bromide staining.

Answer: (d) Both 1 and 3

Explanation:
1. The DNA sample is loaded into the wells, which lie at the negative electrode (cathode) end of the gel.
2. DNA is negatively charged, so it moves toward the positive electrode.
3. So options 1 and 3 are both correct.

Teacher's Note:
1. The wells are at the cathode end because DNA moves to the anode.
2. Small fragments run the farthest.