Test: Biotechnological Applications in Medicine & Industry (NCERT) - NEET MCQ

Human insulin is made up of 51 amino acids arranged in two polypeptide chains: A, having 21 amino acids and B, with 30 amino acids. The two polypeptide chains are interconnected by two disulphide bridges.

Gene therapy is a technique for correcting defective genes responsible for disease development. Under intensive investigation are, disease ranging from the rare genetic diseases caused by single mutations like sickle cell anaemia to killer diseases such as server combined immuno-deficiency (SCID). The first clinical gene therapy was given in 1990 to a 4-years old girl with adenosine deaminase (ADA) deficiency. This enzymes is very important for the immune system to function. ADA deficiency can lead to severe combined immuno-deficiency (SCID).

Recombinant DNA is a form of DNA whose nucleotide sequence has undergone alteration as a result of incorporation of exchange with another DNA strand. In recombinant DNA technology, human genes are often transferred into bacteria or yeast because both bacteria and yeast multiply very fast to form huge population, which expresses the desired gene. By doing so, one can observe the phenotypes of the gene more quickly and in a larger scale than by studying the same traist in humans.

The technique of polymerase chain reaction (PCR) has been applied to detect HIV in suspects AIDS patients and to detect mutations in genes in suspected cancer patients.

DNA fingerprinting technique in which the banding pattern of DNA fragments is compared and can be used in many species, including the human, to indicate relatedness. DNA is digested with restriction enzymes, run on an electrophoretic gel, and blots made from the gel. Such blots are then hybridized with radiolabelled probe DNA consisting of cloned sequences of the short interspersed repeat sequences which are common in vertebrate genomes. Autoradiography provides a distinct banding pattern of DNA fragments containing such DNA sequences.

A represents polypeptide chain C which is removed prior to insulin formation

Using conventional methods of diagnosis (serum and urine analysis, etc.) early detection is not possible. Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA) are some of the techniques that serve the purpose of early diagnosis.

A single stranded DNA or RNA joined with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells. It is followed by detection using autoradiography. The clone having the mutated gene will not appear on the photographic film, because the probe will not have the complementarity with the mutated gene. 

Earlier, insulin used for curing diabetes used to be extracted from pancreas of slaughtered pigs and cattle. This insulin was slightly different from human insulin and caused some undesirable side effects such as allergy. Genetically engineered insulin is a far more efficient.

Gene therapy is a newly emerging branch of biotechnology with tremendous results. It is basically used for correcting genetic disorders. In gene therapy, normal genes are introduced in the cells to replace the missing genes or defective genes. 
Early gene therapy has been proved to be more effective in treating certain brain diseases in humans. They have also shown exemplary results in mice.  
When a child is born, he has its innate immunity, which does not allow any foreign body to settle into its own body easily. But before birth, it has not yet recognized itself, so therapy would be easily accepted.

In 1983, Eli Lilly an American company, first prepared two DNA sequences corresponding to A and B chains of human insulin and introduced them in plasmids of Escherichia coli to produce insulin chains. Chains A and B were produced separately, extracted and combined by creating disulphide bonds to form human insulin (humulin).

As a first step towards gene therapy, lymphocytes from the blood of the patient are grown in a culture outside the body. A functional ADA−cDNA (using a retroviral vector) is then introduced into these lymphocytes, which are subsequently returned to the body of the patient. However, as these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes.

Proteomics is the study of the interactions, function, composition, and structures of proteins and their cellular activities. Proteomics provides a better understanding of the structure and function of the organism than genomics.

Gene therapy is a collection of methods, that allows correction of gene defect that has been diagnosed in a child/embryo. Correcting of a genetic defect involves delivery of a normal gene into the individual or embryo to take over the function of and compensate for the non-functional gene.

For effective treatment of a disease, early diagnosis and understanding its pathophysiology is very important. Using conventional methods of diagnosis (serum and urine analysis, etc.), early detection is not possible. Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA) are some of the techniques that serve the purpose of early diagnosis.

The correct sequence is
1.Synthesis of the gene for human insulin artificially.
2.Insertion of human insulin.
3.Introduction of recombinant plasmid into E.coli
4. Culturing recombinant E.coli in bioreactors.
5.Extraction of a recombinant gene product from E.
6.Purification of Humulin.
So, the correct option is 'i, iv, v, ii, vi, iii'.

Proinsulin is a single polypeptide chain composed of the B and A subunits of insulin joined by the C-peptide region. Proinsulin is converted to insulin during the maturation of secretory vesicles by the action of enzymes.

• (iii) Normal allele is inserted into a retrovirus.


• (i) Retrovirus infects lymphocytes extracted from bone marrow of the patient and cultured.


• (iv) Retrovirus makes a DNA copy of its RNA. This DNA carrying the normal allele gets inserted into the chromosome of the host cell.


• (ii) Engineered cells are injected into patient's bone marrow.

• Step (iii) involves inserting the normal allele into a retrovirus, which will carry the therapeutic gene.


• In step (i), the retrovirus infects lymphocytes extracted from the patient's bone marrow and are cultured.


• After infection, in step (iv), the retrovirus makes a DNA copy of its RNA, which contains the normal allele. This DNA is then inserted into the chromosome of the host cell.


• Finally, in step (ii), the engineered cells with the therapeutic gene are injected back into the patient's bone marrow.

Very low count of bacteria or viruses (when the symptoms of the disease are not yet visible) cab be detected by multiplication of their nucletic acid by PCR (PCR can detect very low amounts of DNA). PCR is usually used to detect HIV in suspected AIDS patients.

Second generation vaccines are the vaccines which are prepared by recombinant DNA technique/ genetic engineering, e.g., hepatitis B virus vaccine, herpes virus vaccine and pneumonia vaccine. The yeast-derived recombinant hepatitis B virus vaccine is the first commercially available human vaccine produced by the genetic engineering technology. Hepatitis B vaccine is produced from transgenic yeast by recombinant DNA technology.