Biology Notes for Class 12
Chapter 12. Biotechnology and Its Applications
Chapter Summary
Biotechnology has given to humans several useful products by using microbes, plant, animals and their metabolic machinery. Recombinant DNA technology has made it possible to engineer microbes, plants and animals such that they have novel capabilities. Genetically Modified Organisms have been created by using methods other than natural methods to transfer one or more genes from one organism to another, generally using techniques such as recombinant DNA technology.
GM plants have been useful in increasing crop yields, reduce postharvest losses and make crops more tolerant of stresses. There are several GM crop plants with improved nutritional value of foods and reduced the reliance on chemical pesticides (pest-resistant crops).
Recombinant DNA technological processes have made immense impact in the area of healthcare by enabling mass production of safe and more effective therapeutics. Since the recombinant therapeutics are identical to human proteins, they do not induce unwanted immunological responses and are free from risk of infection as was observed in case of similar products isolated from non-human sources. Human insulin is made in bacteria yet its structure is absolutely identical to that of the natural molecule.
Transgenic animals are also used to understand how genes contribute to the development of a disease by serving as models for human diseases, such as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer’s.
Gene therapy is the insertion of genes into an individual’s cells and tissues to treat diseases especially hereditary diseases. It does so by replacing a defective mutant allele with a functional one or gene targeting which involves gene amplification. Viruses that attack their hosts and introduce their genetic material into the host cell as part of their replication cycle are used as vectors to transfer healthy genes or more recently portions of genes.
The current interest in the manipulation of microbes, plants, and animals has raised serious ethical questions.
Biotechnological Applications in Agriculture:
Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO).
Advantages of Genetic Modification in plants.
Ø Made crops more tolerant to abiotic stresses (cold, drought, salt, heat)
Ø Reduce reliance on chemical pesticides (pest resistant crop)
Ø Helped to reduce post harvest losses.
Ø Increased efficiency of mineral usage by plants.
Enhanced nutritional values of food e.g. vitamin A.
Bt Cotton:
Ø Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes).
Ø B.thuringiensis forms protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein.
Ø These proteins are present in inactive protoxin form, but become active toxin in the alkaline pH of insect gut.
Ø The activated toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and eventually cause death of insect.
Ø Specific Bt toxin genes were isolated form B. thuringiensis and genetically transferred to several plants such as cotton.
Ø Crystal proteins are produced by a gene called cry in B. thuringiensis.
Ø The protein coded by genes cryIAc and cryIIAb control the cotton bollworms.
Ø The protein coded by gene cryIAb controls corn borer.
Pest resistant plants:
Ø Several nematodes parasitize a wide variety of plants and animals including human beings.
Ø A nematode Meloidegyne incognitia infects the root of tobacco plants and causes a great reduction in yield.
Ø Strategy based on RNA interference (RNAi) prevents this infestation.
Ø Process by which double-stranded RNA (dsRNA) directs sequence-specific degradation of mRNA.
Steps of RNA interference:
Ø Double stranded RNA is produced endogenously or exogenously.
Ø Using Agrobacterium vectors nematode specific genes were introduced into the host plant (tobacco plant).
Ø Introduction of DNA produces both sense and antisense RNA in the host.
Ø These two RNA’s being complementary to each other formed a double stranded (dsRNA) that initiated RNAi.
Ø The dsRNA injected into the host plant from outside called exogenous dsRNA.
Ø The dsRNAs are cleaved into 21-23 nt segments (“small interfering RNAs”, or siRNAs) by an enzyme called Dicer.
Ø siRNAs are incorporated into RNA-induced silencing complex (RISC)
Ø Guided by base complementarity of the siRNA, the RISC targets mRNA for degradation.
Ø The consequence was that the parasite could not survive in a transgenic host.
Biotechnological Applications in Medicine:
Ø Biotechnology enables mass production of safe and more effective therapeutic drugs.
Ø Recombinant therapeutics does not induce unwanted immunological responses as is common in case of similar products isolated from non-human sources.
Ø At present around 30 recombinant therapeutics, approved for human-use.
Genetically Engineered Insulin:
Origin of replication:
Ø Taking insulin at regular interval of time is required for adult-onset diabetes.
Ø Previously the source of insulin was the slaughtered cattle and pigs.
Ø This insulin caused allergy in some patients.
Ø Each insulin made of two short polypeptide chains; chain A and chain B that are linked together by disulphide linkage.
Ø Insulin synthesized in pancreas as pro-hormone which is a single polypeptide with an extra stretch called C-peptide.
Ø C-peptide is removed during matured insulin.
Ø In 1983 Eli Lilly an American company prepared two DNA sequences corresponding to A and B, chains of human insulin and introduced them in plasmids of E.coli to produce insulin chains.
Ø Chain A and chain B produced separately, extracted and combined by creating disulfide bonds to form mature human insulin.
Gene therapy:
Ø Gene therapy is an attempt to cure hereditary or genetic diseases.
Ø Genes are inserted into a person’s cells and tissue to treat the disease.
Ø The first clinical gene therapy was given in 1990 to a 4-yr old girl with adenosine deaminase (ADA) deficiency.
Ø This enzyme is required for breakdown of deoxyadenosine into uric acids.
Ø In the absence of ADA toxic deoxyadenosine is accumulated and destroy the infection fighting immune cells called T-cells and B-cells.
Ø This disorder is caused due to the deletion of the gene for adenosine deaminase in chromosome 20.
Treatment:
Ø Treated by bone marrow transplantation.
Ø Enzyme replacement therapy, involving repeated injections of the ADA enzyme.
Ø Lymphocytes from the blood of the patient are grown in a culture. A functional ADA cDNA is then introduced into these lymphocytes and returned into the body.
Ø The patient required periodic infusion of genetically engineered lymphocytes because these cells are not immortal.
Ø Functional ADA cDNA introduced into cells at early embryonic stages, could be the permanent cure.
Molecular diagnosis:
Ø Early detection of disease is not possible by conventional methods (serum and urine analysis).
Molecular diagnosis techniques:
Ø Recombinant DNA technology.
Ø Polymerase chain reaction (PCR)
Ø Enzyme linked Immuno-sorbent Assay (ELISA).
Ø Very low concentration of a bacteria or virus can be amplified and detected by PCR.
Ø It used to detect genetic disorders.
Ø PCR is use full to mutation in genes in suspected cancerous patient:
- A single stranded DNA or RNA tagged with radioactive molecule (probe) is allowed to hybridize to its complementary DNA in a clone of cells followed by detection using autoradiography.
- The clone having mutated gene unable make complementary bonding of probe, hence not appears in photographic film.
TRANSGENIC ANIMALS:
Ø Animals that have an alien DNA which able to express in it is called transgenic animals.
Reasons for creation of transgenic animals:
i. Normal physiology and development:
Ø Transgenic animals are specifically designed to allow study of:
- How the genes are regulated.
- How the gene affects normal functioning of body
- How it affects growth and development. E.g. insulin like growth factor.
Ø The animals made transgenic to know the biological effect and result.
i. Normal physiology and development:
Ø Isolation of DNA ,
Ø Fragmentation of DNA by restriction endonuclease.
Ø Isolation of desired DNA fragment by gel electrophoresis.
Ø Ligation of DNA fragment with a vector by DNA ligase.
Ø Transferring the recombinant DNA into the host.
Ø Culturing the host cells in a medium at large scale in a bioreactor.
Ø Extraction of desired product by downstream processing.
ii. Study of disease:
Ø Transgenic animals are designed to understand how genes contribute to the development of disease like cancers, cystic fibrosis, rheumatoid arthritis and Alzheimer’s.
iii. Biological products:
Ø Transgenic animals are used to produce biological product of human interest:
- α-1-antitrypsin used to treat emphysema.
- Proteins for treatment for PKU and cystic fibrosis.
- Transgenic cow Rosie, produce human protein enriched milk (2.4 gm/lit. human α- lactalbumin)
iv. Vaccine safety:
Ø Transgenic mice are being developed and use in testing the safety of vaccines before they are used for humans.
Ø Polio vaccine is tested in mice.
v. Chemical safety testing:
Ø This is also known as toxicity/safety testing.
Ø Transgenic animals are made to known the effect of toxic chemicals.
Ethical Issues:
Ø GEAC (Genetic Engineering Approval Committee) set up by Indian Govt, which will make decisions regarding validity of GM research and safety of introducing GM-organisms for public services.
Ø A patent is the right granted by a government to an inventor to prevent others from commercial use of his invention.
Ø Patents granted for biological entities and for products derived from them; these patents are called biopatents.
Ø 27 documented varieties of Basmati are grown in India.
Ø Biopiracy is the term used to refer to the use/exploit or patent, of biological resources by multinational companies and other organizations without proper authorization from the countries and people concerned without compensatory payment.
Disclaimer: All contents are originally prepared by Shri K C Meena Ji, Principal, KVS.
Amazon Affiliate Disclaimer: cbsecontent.com is a part of Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.in. As an amazon associates we earn from qualifying purchases.