31 Years NEET Previous Year Questions: Biotechnology & Its Applications

However, very low concentration of a bacteria or virus (at a time when the symptoms of the disease are not yet visible) can be detected by amplification of their nucleic acid by PCR. It is being used to detect mutations in genes in suspected cancer patients too.

The functional insulin molecule has two chains A and chain B, that are linked together by disulphide bridges and not hydrogen bonds.

Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans and dipterans. B. thuringiensis forms protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein which exists as inactive protoxins but once an insect ingest the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilise the crystals.

Retroviruses cause cancer in animals including humans. So modified retroviruses are used to transfer desirable genes into animal cells. It is used in gene therapy, in which lymphocytes from blood of patient are taken and grown in culture medium outside the body, a functional gene is introduced by using a retroviral vector into these lymphocytes which are again reintroduced into the patient body.

Gene therapy is a technique of genetic engineering which involves replacement of a faulty/disease causing gene by a normal healthy functional gene. The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. This enzyme is very important for the immune system to function. The deficiency of this enzyme can lead to severe combined immune deficiency (SCID).

Bt cotton is being grown in India by the farmers. Bt cotton is pest resistant plant which could decreased the pesticides used. Bt toxin is produced by a bacterium Bacillus thusringiensis (Bt for short). Bt toxin gene has been cloned from the bacteria and been expressed in  plants to provide resistance to insects without the need for insecticides.

Gene therapy is an experimental technique that uses genes to treat or prevent disease. The first clinical gene therapy was given for treating adenosine deaminase deficiency. A four-year old girl became the first gene therapy patient on September 14, 1990 at the NIH Clinical Center. Adenosine deaminase deficiency, also called ADA deficiency or ADASCID is an autosomal recessive metabolic disorder that causes immunodeficiency. ADA deficiency is due to a lack of the enzyme adenosine deaminase.

RNA interference technique, sense & antisense RNA fused to form dsRNA that silent the expression of m- RNA of nematode. RNA interference is a novel strategy adopted to prevent infestation of nematode Meloidegyne incognitia in roots of tobacco plants. 

Golden rice is a variety of Oryza sativa rice produced through genetic engineering to biosynthesise beta-carotene, a precursor of vitamin-A in the edible part of rice (i.e. endosperm). The research that led to golden rice was conducted with the goal of helping children who suffer from vitamin-A deficiency. Because many children in countries where there is a dietary deficiency in vitamin-A rely on rice as a staple food, the genetic modification of rice to produce the vitamin-A precursor beta-carotene is seen as a simple and less expensive alternative to vitamin supplements.

Recombinant DNA technology is the process joining together two  DNA molecules from two different species that are inserted into a host organism to produce new genetic combination.

Common activities in bioinformatics include mapping and analysing DNA and protein sequences, aligning different DNA etc are the part of human genome project.

In this technique nematode specific genes are introduced in the host plant in such a way that it produces both sense and antisense RNA. The two RNA’s being complementary to each other from a double stranded RNA (dsRNA) which is also called interfering RNA responsible for initiating RNA interference (RNA i). This (dsRNA) bind to and prevent translation of specific mRNA of nematode (gene silencing). Thus transgenic plants based on RNAi technology are resistant to nematode.

A fed batch is a biotechnological batch process which is based on feeding of a growth limiting nutrient substrate to culture. It is done for purifying enzymes.

In the world maximum num ber of existing transgenic animals is mice.

Molasses are commonly used in distillaries for the production of ethanol. The molasses is diluted to a mash containing 10-20 wt % of sugar. By the fermentation system of molasses ethanol can be produced.

Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into cotton plant to form a genetically modified crop called Bt cotton. Bt cotton has high yield and resistance to bollworms.

Genetic engineering has been successfully used for producing transgenic mice. Many transgenic mice are designed to increase our understanding of how genes contribute to development of diseases. Transgenic mice are being developed for use in testing the safety of vaccine before they are used in human beings. For example transgenic mice are being used to test the safety of polio vaccine.

The genetically modified brinjal in India has been developed for insect resistance. Bt brinjal is a transgenic brinjal that is developed by inserting a crystal gene from the Bacillus thuringiensis into the brinjal’s genome. This process of insertion is accomplished using Agrobacterium mediated recombination.

Transgenic plants are the ones generated by introducing foreign DNA into a cell and regenerating a plant from that cell.

About Bt toxin, it is true, that the inactive protoxin gets converted into active form in the insect gut. There are several advantages in expressing Bt toxins in transgenic Bt crops. The level of toxin expression can be very high, thus delivering sufficient dosage to the pest.
The toxin expression is contained within the plant system and hence only those insects that feed on the crop perish. The toxin expression can be modulated by using tissue-specific promoters and replaces the use of synthetic pesticides in the environment.

Agrobacterium tumefaciens is the causal agent of crown gall disease (the formation of tumours) in over 140 species of dicot. This disease caused by a DNA plasmid (Ti plasmid) carried by bacterium and transferred to the plant cells. Ti plasmid has widely used in plant engineering as a vector in order to inject gene in host plant to form transgenic plant.

As of 1999, the most prevalent GM trait was glyphosate resistance (pesticide). This herbicide used on grain and grass crops were highly toxic and not effective against narrow-leaved weeds. Thus, developing crops that could withstand spraying with glyphosate would both reduce environmental and health risks. Tobacco plants have been engineered to be resistant to the herbicide bromoxynil. Crops have been commercialized that are resistant to the herbicide glufosinate also. The main objective of these herbicide-resistant GM crops is that it reduces the accumulation of herbicides in the food articles for health safety.

Golden rice is a transgenic food crop which  may help in solving the problem of night blindness in developing countries. Golden rice or miracle rice is rich in vitamin A or β-carotene and iron and decaffeinated coffee are also valuable achievements of gene transfer technology. 

Bt cotton, a transgenic crop variety has been introduced in India. The Bt cotton variety contains a foreign gene obtained from Bacillus thuringiensis. This bacterial gene protects cotton from the ball worm, a major pest of cotton.

The term Green revolution refers to the very substantial increase in yield obtained by breeding high yielding varieties of crops, under intensive application of fertilizers, irrigation and pesticides. The world wide increase, in productivity has come to be known as the ‘Green Revolution’ for which Dr. Borlaug won the Noble Peace Prize in 1970.

Golden rice is a transgenic crop of the future with high Vit. A content. Millions of people suffer from Vit. A deficiency which leads to vision impairment. Transgenic rice has been developed which is capable of synthesizing beta carotene, the precursor of Vitamin A. The rice variety is now being crossed into adapted varieties with field tests possible in an year or two.

ELISA test is a technique which can detect any amount of an antibody or antigen with the help of an enzyme. The commonly used enzymes are alkaline phosphatase and peroxidase.

Cultured animal cells are used in the production of vaccines producing viruses. Vaccines for polio, rabies, chicken pox, measles and   hepatitis B are produced using animal cell culture. Insulin production includes insertion of chemically synthesized A and B chain DNA sequences into plasmids followed by transformation of E. coli with plasmid carrying the gene. Replication of recombinant plasmid in E. coli produces insulin. Interferon is a carbohydrate containing proteins that are produced by fibroblasts and leukocytes in response to immune stimuli. It has antiviral and anticancer properties and is produced by transformation of E. coli with recombinant plasmid carrying the gene for interferon. Edible proteins are produced by molecular farming, i.e., transfer of genes of proteins to plants and animals for production of proteins. 

Monoclonal antibodies are identical molecules specific for one type of antigen. These are obtained by injecting the target antigen into a rat or mouse. Sometimes later, the spleen cells producing antibodies are isolated and fused with myeloma cells to produce monoclonal antibodies.

Human insulin has 53 amino acids in two polypeptides (A and B) connected by two S -S (disulphide) linkages. In 1983, American company Eli Lilly prepared two DNA sequences corresponding to A and B insulin chains. When  introduced in plamids of  E.coli, insulin chains were formed. They were extracted and fused to produce humulin (human insulin).