Test: Biotechnology & its Application - NEET MCQ

The cry gene of Bacillus thuringiensis produces a protein, that forms crystalline inclusions i.e., is crystal in nature in the bacterial spores. Due to their crystal nature these proteins are named ‘cry’ proteins and are responsible for the insecticidal activities of the bacterial strains. In alkaline environment of insect midgut ‘Cry’ proteins are solubilized. Then to release core toxic fragments these proteins undergo proteolytic digestion.These toxins bind to receptors in brush border of midgut epithelial cells. As a result, brush border, membrane develop pores, most likely nonspecific in nature and cause influx of ions and water into the cells resulting in their swelling and eventual lysis. 

A soil bacterium Bacillus thuringiensis (Bt) produces a Cry protein (crystal protein). This protein is toxic to the larvae of certain insects. There are several kinds of Cry proteins, which are is toxic to a different group of insects. The gene encoding Cry protein, that is cry gene has been isolated and transferred into several crops. A crop expressing a cry gene is usually resistant to the groups of insects. 

Plant tissue culture has various applications in the different fiields of biology. An example of this is the production of transgenic plants and animals. Transgenic organisms contain genes, which are transferred into them through the genetic engineering. These genes are known as transgenic. 

Bacillus thuringiensis (Bt), a soil bacterium produces a Cry protein (crystal protein). This protein is toxic to the larvae of certain insects. There are several kinds of Cry proteins. Each Cry protein is toxic to a different group of insects. The gene encoding Cry protein, i.e., cry gene has been isolated and transferred into several crops. A crop expressing a cry gens is usually resistant to the groups of insects. 

 FlavrSavr is a transgenic tomato variety. Fruits of this variety remain fresh and retain their flavour for much longer than normal fruits. It happens due to the blockage of the production of pectin degrading enzyme polygalacturonase. 

Genetically modified tomato i.e., flavr savr show delayed ripening. By the use of antisense RNA technology the enzyme polygalacturonase, that causes damage to pectin is deactivated and for longer duration the tomato is kept fresh. 

RNAi (RNA interference) occurs in all eukaryotic organisms as a method of cellular defense. This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to specific mRNA and prevents translation of the mRNA. To induce RNA interference in any organism in vitro there are two methods,  the complementary RNA can be synthesized and then annealed to produce dsRNA and inserted into cells or the cells are genetically modified to produce the two complementary RNA strands or duplex form in vivo by transcription. However, the first method i.e., in vitro insertion of synthesized complementary RNA stops target gene expression for only 4-6 days and their re-introduction is required. But the second method i.e., the vector DNA construct once transfected into the cells, will keep on generating RNA interference and hence, cause a permanent inhibition of the damage. 

 RNAi is the silencing of a specific mRNA. 

 Meloidogyne incognita infects the root of tobacco plant that leads to the degradation of cell walls of the roots and reduce the yield. 

 By inserting genes (or desired protein products transgenic micro-organisms can be developed using recombinant DNA technology. These transgenic organisms acts as living microfactories that produce proteins like human insulin, human growth hormone, etc. Production of proteins from such organisms is easier, more efficient and cost effective

Adult onset diabetes management is possible by taking insulin at regular time intervals, but insulin from other animals could elicit immune response in body. Biotechnology has helped to overcome this problem. Transgenic bacteria have been produced that translate the constituting polypeptide chains of human insulin from the bacterial cells. These polypeptides can be extracted and combined to produce human insulin, by creating disulfide bonds. In humans, insulin is produced as a prohormone with three polypeptides A, B and C. After processing, the C peptide is removed and mature insulin is formed. When transgenic bacteria are used, instead of producing extra stretch of C peptide, only A and B polypeptides are produced and then linked directly to produce mature insulin. 

ADA disorder is caused because of lack of gene for adenosine deaminase. It affects the human immune system. 

 The ADA gene gives instructions for producing the enzyme adenosine deaminase. In all cells this enzyme is produced, but the highest levels of adenosine deaminase takes place in immune system cells called lymphocytes, that develop in lymphoid tissues. Lymphocytes form the immune system, that defends the body against potentially harmful invaders, such as viruses or bacteria. 

 Transgenic organisms contain genes, that are transferred into them through the genetic engineering. These genes are called transgenes. Using recombinant DNA technology transgenic organisms can be produced. 

Those organisms that have their genetic material modified to meet some desired conditions are genetically modified (GM) organisms. They generally carry a foreign gene in their DNA. GM salmon was the first transgenic animal for food production. It was produced by fusion of normal ova (eggs) with genetically modified sperms. The zygotes with modified gene developed into embryos that gave rise to much bigger adults than either parent thus have greater food value. It is achieved by addition of a gene that codes for the growth hormone that allows the fish to grow larger more rapidly than the non-transgenic salmon. 

 Several animal studies indicate serious health risks associated with genetically modified (GM) food including infertility, immune problems,accelerated aging, faulty insulin regulation, and changes in major organs and the gastrointestinal system. The bacteria in the alimentary canal become resistant to antibiotic by taking up the resistant gene present in GM foods. 

Palmiter and Brinster (1981) developed the first transgenic animal ‘supermouse’. It has human growth hormone gene. It has been intoroduced and expressed. Size of supermouse is big in size than the normal mouse. 

 Improved resistance to drought, salinity and extreme temperatures has been observed in transgenic plants that express/ over express genes regulating osmolytes, specific proteins, antioxidants, ion homeostasis, transcription factors and membrane composition. Many plants genome are altered by combining them with other genes in order to get desired traits. 

 Hirudin is a protein that prevents blood clotting. The gene responsible for the production of blood clotting preventing protein have been chemically synthesised and then transferred into Brassica napus (Brassicaceae). Hirudin protein accumulates in the seeds of this plant.

Humulin is the first genetically engineered pharmaceutical product. It is better than conventional insulin because conventional insulin produces many side effects over a long period.