Solved Exercise, Bio-12, Ch-23


(i) The use of polymerase chain reaction (PCR) creates a _______ of copies in a laboratory test tube. (lesser number)

(ii) _______ free living organisms in the environment that have had a foreign gene inserted into them. (transgenic organisms)

(iii) _______ are known sequences of DNA that are used to find complementary DNA strands; can be used diagnostically to determine the presence of particular gene. (Probes)

(iv) _______ is production of many identical copies of a gene. (Gene cloning)

(v) _______ is self-duplicating ring of accessory DNA in the cytoplasm of bacteria. (plasmid)


(i) Which of these is a true statement?

(a)  Both plasmid and viruses can serve as vector

(b)  Only gene therapy uses vector

(c)  Plasmid can carry recombinant DNA but viruses can not

(d)  Vector carry only the foreign gene into the host cell

(e)  Both (a) and (d) are correct

EXPLANATION: Both plasmids and viruses can serve as vectors in genetic engineering to introduce foreign genes into host cells. Moreover, vectors carry only the foreign gene into the host cell, whether they are plasmids or viruses.

(ii) Which of these is a benefit to having insulin produced by biotechnology?

(a)  It is just as effective

(b)  It can be mass produced

(c)  It is non allergenic

(d)  It is less expensive

(e)  All of these are correct

EXPLANATION: (a) Insulin produced by biotechnology is just as effective as naturally occurring insulin. (b) Biotechnological methods allow for the mass production of insulin, addressing the demand. (c) Insulin produced through biotechnology is typically non-allergenic. (d) Biotechnological production methods can lead to a more cost-effective production of insulin compared to traditional methods.

(iii) Restriction fragment length polymorphism (RFLPs)

(a)  Are achieved by using restriction enzymes

(b)  Are the basis for DNA finger prints

(c)  Identify individuals genetically

(d)  Can be subjected to gel electrophoresis

(e)  All of these are correct

EXPLANATION: (a) RFLPs are achieved by using restriction enzymes to cleave DNA at specific recognition sites. (b) RFLPs form the basis for DNA fingerprints, as variations in the lengths of restriction fragments can be analyzed. (c) RFLPs can be used to identify individuals genetically by comparing the unique patterns of fragments. (d) RFLPs can be subjected to gel electrophoresis, a technique used to separate DNA fragments based on size.

(iv) Which of these would you not expect to be a biotechnology product?

(a)  Vaccine

(b)  Modified enzyme

(c)  DNA probes

(d)  Protein hormones

(e)  Steroid hormone

EXPLANATION: Steroid hormones are often chemically synthesized or extracted from natural sources, but they are not typically produced through biotechnological processes involving genetic manipulation or cellular systems.

(v) What is the benefit of using a retrovirus as a vector in gene therapy?

(a)  It is not able to enter cells

(b)  It incorporates the foreign gene into the host chromosome

(c)  It eliminates a lot of unnecessary steps

(d)  It prevents infection by other viruses

(e)  Both (b) and (c) are correct

EXPLANATION: (b) Retroviruses integrate their genetic material into the host chromosome, ensuring stable and long-term expression of the foreign gene. (c) Using retroviruses simplifies the process of introducing the foreign gene into the host cell, eliminating some unnecessary steps.

(vi) Gel electrophoresis.

(a)  Cannot be used on nucleotides

(b)  Measure the size of plasmids

(c)  Tells whether viruses are infectious

(d)  Measure the change and size of proteins and DNA fragments

(e)  All of these are correct

EXPLANATION: Gel electrophoresis separates molecules based on their size and charge, allowing for the measurement of proteins and DNA fragments.

(vii) Which of these is incorrectly matched?

(a)  Protoplast — plant cell engineering

(b)  RFLPS — DNA finger printing

(c)  DNA polymerase — PCR

(d)  DNA ligase — mapping human chromosomes

EXPLANATION: DNA ligase is primarily involved in sealing nicks in DNA strands and is not directly used for mapping human chromosomes. Mapping human chromosomes involves other techniques such as fluorescence in situ hybridization (FISH).


Transgenic animals that secrete a specific product are often cloned to generate multiple individuals with the desired genetic trait. This enables large-scale production of the desired substance, such as a therapeutic protein, hormone or an enzyme, in the animal’s milk or eggs. Cloning ensures that every offspring shall inherit the introduced gene, and express the desired product consistently.

Primary Goals of Human Genome Project:

(1) The first goal is to construct a genetic map of the human genome. The aim is to show the sequence of genes along the length of each type of chromosome.

(2) The second goal is to construct a base sequence map. There are three billion base pairs in the human genome and it is estimated it could take an encyclopedia of 200 volumes, each with 1000 pages, to list all of these.

Benefits of Project:

Knowing the base sequence of normal genes may make it possible one day to treat certain human ills by administering normal genes and or their protein products to those who suffer from a genetic disease.

Ex Vivo Gene Therapy:

Definition: Removes cells from a patient, modifies them to insert a functional copy of a missing or defective gene, and then reintroduces the modified cells back into the patient.

Example: X-linked SCID (Severe Combined Immunodeficiency) treatment. Blood stem cells are extracted from the patient, genetically modified to include a functional immune system gene, and then reintroduced into the patient’s body.

In Vivo Gene Therapy:

Definition: Delivers functional copies of genes directly into a patient’s target cells within the body using vectors like viruses.

Example: Cystic fibrosis treatment. A modified virus carrying a healthy copy of the CFTR gene is delivered to lung cells via inhalation, aiming to correct the genetic defect and improve lung function.


Consult textbook at page 204 — 205.

Consult textbook at page 205 — 206.

Consult textbook at page 206 — 207.

Consult textbook at page 207 — 209.

Consult textbook at page 211 — 214.

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