"Biotechnology: Principles and Applications" — Practice

Question 1

Restriction endonucleases are also known as:
(a) molecular scissors (b) molecular glue (c) molecular pumps (d) molecular motors

Accepted Answer

(a) molecular scissors.

Restriction endonucleases cut DNA at specific palindromic recognition sequences, earning them the name 'molecular scissors' — the essential tool of genetic engineering.

Question 2

In the restriction enzyme name EcoRI, the letter 'R' denotes:
(a) the bacterial strain (b) the species (c) the genus (d) the order of discovery

Accepted Answer

(a) the bacterial strain.

EcoRI: 'E' = genus Escherichia, 'co' = species coli, 'R' = strain, 'I' = order of discovery (first enzyme isolated from that strain).

Question 3

A DNA sequence that reads the same in the 5'→3' direction on both strands is called:
(a) palindromic (b) complementary (c) antiparallel (d) polymorphic

Accepted Answer

(a) palindromic.

Restriction enzymes recognise palindromic sequences, e.g., GAATTC/CTTAAG for EcoRI — each strand reads GAATTC 5'→3'.

Question 4

Which of the following is NOT a requirement of a good cloning vector?
(a) multiple recognition sites for the same restriction enzyme (b) an origin of replication (c) a selectable marker (d) small size for easy manipulation

Accepted Answer

(a) multiple recognition sites for the same restriction enzyme.

A vector should ideally have a SINGLE (unique) recognition site for a commonly used enzyme; an ori, selectable marker, and small size are all genuine requirements.

Question 5

Insertional inactivation is used to identify recombinant bacterial colonies by:
(a) loss of function of one selectable marker gene (b) gain of a new antibiotic resistance (c) change in colony colour to blue (d) increased growth rate

Accepted Answer

(a) loss of function of one selectable marker gene.

Foreign DNA inserted into a marker gene disrupts it; recombinants lose that specific marker's phenotype (e.g., antibiotic resistance) while retaining the other, allowing them to be distinguished from non-recombinants.

Question 6

In agarose gel electrophoresis, DNA fragments move toward the anode because:
(a) DNA is negatively charged (b) DNA is positively charged (c) DNA has no charge (d) the anode attracts all molecules regardless of charge

Accepted Answer

(a) DNA is negatively charged.

The phosphate backbone gives DNA an overall negative charge, so fragments migrate toward the positive electrode (anode); smaller fragments move faster and farther through the agarose matrix.

Question 7

In the recombinant DNA technology process, ligation of the gene of interest into a vector occurs:
(a) after cutting with restriction enzymes and before transformation into the host (b) before isolation of DNA (c) after transformation into the host (d) simultaneous with culturing the host

Accepted Answer

(a) after cutting with restriction enzymes and before transformation into the host.

The sequence is: isolate DNA → cut with restriction enzyme → (amplify via PCR if needed) → ligate into vector using DNA ligase → transform into host cell → culture host and extract product.

Question 8

The thermostable DNA polymerase used in PCR is isolated from:
(a) Thermus aquaticus (b) Escherichia coli (c) Bacillus thuringiensis (d) Agrobacterium tumefaciens

Accepted Answer

(a) Thermus aquaticus.

Taq polymerase, from the hot-spring bacterium Thermus aquaticus, remains active at the ~95°C used during the denaturation step of each PCR cycle, unlike ordinary DNA polymerase.

Question 9

The correct order of steps in one PCR cycle is:
(a) denaturation → annealing → extension (b) annealing → denaturation → extension (c) extension → denaturation → annealing (d) denaturation → extension → annealing

Accepted Answer

(a) denaturation → annealing → extension.

The DNA is first denatured (strands separate at ~95°C), primers anneal to flanking sequences (~50–65°C), then Taq polymerase extends new strands (~72°C).

Question 10

Humulin, the first genetically engineered human insulin, was produced by:
(a) expressing chains A and B separately in E. coli and then combining them via disulfide bonds (b) extracting insulin from genetically modified pigs (c) expressing the full proinsulin gene directly in yeast (d) chemical synthesis without any bacterial host

Accepted Answer

(a) expressing chains A and B separately in E. coli and then combining them via disulfide bonds.

Eli Lilly introduced DNA sequences for insulin chain A (21 amino acids) and chain B (30 amino acids) into separate E. coli strains, then extracted and combined the chains by forming disulfide bridges to produce humulin.

Question 11

The first disease for which gene therapy was successfully attempted is:
(a) ADA deficiency (SCID) (b) sickle-cell anaemia (c) haemophilia (d) cystic fibrosis

Accepted Answer

(a) ADA deficiency (SCID).

Adenosine deaminase (ADA) deficiency, a form of severe combined immunodeficiency, was the first condition treated with gene therapy — a functional ADA gene was introduced into the patient's lymphocytes via a retroviral vector.

Question 12

Gene therapy using genetically engineered lymphocytes for ADA deficiency requires periodic reinfusion because:
(a) lymphocytes are not immortal cells (b) the ADA gene degrades within hours (c) lymphocytes cannot be cultured outside the body (d) retroviral vectors are unstable at body temperature

Accepted Answer

(a) lymphocytes are not immortal cells.

Engineered lymphocytes eventually die off, so periodic infusions of freshly engineered lymphocytes are required. A permanent cure would need the gene introduced into totipotent embryonic stem cells, which raises separate ethical concerns.

Question 13

The Bt toxin produced by Bacillus thuringiensis is activated in the target insect due to:
(a) the alkaline pH of the insect gut (b) the acidic pH of the insect gut (c) high temperature inside the insect body (d) enzymatic action in the plant tissue

Accepted Answer

(a) the alkaline pH of the insect gut.

The Bt toxin is stored as an inactive protoxin; the insect's alkaline gut pH solubilises and activates it, allowing it to bind the gut epithelium and create pores that kill the insect — explaining why it doesn't harm the plant.

Question 14

Tobacco plants were made resistant to the nematode Meloidogyne incognita using which technique?
(a) RNA interference (RNAi) (b) Bt toxin expression (c) antisense DNA insertion into the nematode genome (d) CRISPR gene editing

Accepted Answer

(a) RNA interference (RNAi).

A nematode-specific gene was introduced into tobacco via Agrobacterium tumefaciens vectors; the resulting double-stranded RNA (sense + antisense) triggers RNAi, silencing the nematode's own mRNA when it feeds on the plant, preventing infestation.

Question 15

In India, the body responsible for approving the release of genetically modified organisms (including field trials) is:
(a) GEAC (Genetic Engineering Approval Committee) (b) ICMR (c) UGC (d) FSSAI

Accepted Answer

(a) GEAC (Genetic Engineering Approval Committee).

GEAC evaluates the safety and validity of GM research and decides on the introduction of GM organisms (including Bt crops) for public/commercial use in India.

Practice — "Biotechnology: Principles and Applications"

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