Sunday, December 27, 2020

Biotechnology and its Applications | Plus 2 Botany | Exam Capsule Notes

BIOTECHNOLOGY & ITS APPLICATIONS: 
CHAPTER AT A GLANCE

APPLICATIONS IN AGRICULTURE

Genetically Modified Organisms (GMO): Organisms whose genes are altered by manipulation.

Advantages of genetic modification in plants:
  • It makes crops more tolerant to abiotic stresses.
  • Reduce the use of chemical pesticides.
  • Reduce post-harvest losses.
  • Increases efficiency of mineral usage by plants.
  • High nutritional value. E.g. Golden rice (Vitamin A rich).
Pest Resistant Plants: Act as bio-pesticide. E.g. Bt cotton, Bt corn, rice, tomato, potato, soyabean etc.

Bt Cotton:

B. thuringiensis forms a toxic insecticidal protein (Bt toxin).

When an insect ingests the toxin, it becomes active.

Bt toxin genes from B. thuringiensis incorporated into crop plants such as cotton.

Bt toxin is coded by cry genes. E.g. cryIAc & cryIIAb genes control cotton bollworms. CryIAb controls corn borer.

Nematode resistance in tobacco plants:

A nematode Meloidogyne incognitia infects roots of tobacco plants. It can be prevented by RNA interference (RNAi).

RNAi is a cellular defense in eukaryotes. It prevents translation of an mRNA (silencing) due to a dsRNA molecule.

Using Agrobacterium vectors, nematode-specific genes are introduced into host plant → produces sense & anti-sense RNA in host cells → They form double stranded (ds) RNA → initiates RNAi and silences specific mRNA of nematode → parasite cannot survive in a transgenic host.

APPLICATIONS IN MEDICINE

To produce therapeutic drugs.

Recombinant therapeutics does not have unwanted immunological responses.

1. Genetically Engineered Insulin

Human insulin is produced using bacteria.

In mammals, insulin is synthesized as a pro-hormone (pro-insulin).

The pro-hormone contains an extra stretch called C peptide. This is removed during maturation into insulin.


An American company Eli Lilly prepared two DNA sequences corresponding to A & B polypeptide chains of human insulin and introduced in E. coli plasmids to produce human insulin.

2. Gene Therapy

It is a method to correct a gene defect in a child/embryo.

First clinical gene therapy was to treat adenosine deaminase (ADA) deficiency. This is caused due to the deletion of the gene for adenosine deaminase.

Gene therapy for ADA deficiency:

Collect lymphocytes from the patient’s blood and grow in a culture → Introduce a functional ADA cDNA into lymphocytes (using a retroviral vector) → They are returned to the patient.

If the ADA gene is introduced into cells at early embryonic stages, it could be a permanent cure.

3. Molecular Diagnosis

For early diagnosis of diseases. E.g. PCR, ELISA.

PCR (Polymerase Chain Reaction):
  • Very low concentration of a bacteria or virus can be detected by amplification of their nucleic acid by PCR.
  • Uses of PCR: To detect HIV and genetic disorders. To detect gene mutations in suspected cancer patients.
  • A single stranded DNA or RNA, tagged with a radioactive molecule (probe) is hybridized to its complementary DNA in a clone of cells. It is detected by autoradiography. The clone having mutated gene will not appear on the photographic film, because the probe will not have complementarity with the mutated gene.
ELISA (Enzyme Linked Immuno-Sorbent Assay):
  • It is based on the principle of antigen-antibody interaction.
  • Infection by pathogen can be detected by the presence of antigens or by antibodies synthesized against pathogen.

TRANSGENIC ANIMALS

The animals whose genome was altered by introducing a foreign gene by manipulation. E.g. Transgenic rats, rabbits, pigs, cow etc.

Benefits of transgenic animals:
  • To study regulation of genes and their action on normal physiology & development: E.g. Study of insulin-like growth factor.
  • To study disease-causing genes and their treatments: E.g. transgenic models for cancer, cystic fibrosis, rheumatoid arthritis & Alzheimer’s.
  • To produce biological products: E.g. human protein (a-1-antitrypsin) used to treat emphysema. Rosie (first transgenic cow) produced human protein-enriched milk. It contains human a-lactalbumin and is more balanced product for human babies than cow-milk.
  • Vaccine safety testing: Transgenic mice are used to test the safety of the polio vaccine.
  • Chemical safety testing (toxicity testing): Some transgenic animals carry genes which make them more sensitive to toxic substances than non-transgenic animals.

ETHICAL ISSUES

  • Problem of unpredictable results: Indian Government has set up GEAC (Genetic Engineering Approval Committee) to make decisions about validity and safety of GM research & GM-organisms.
  • Biopiracy: It is the use of bio-resources without proper authorization. E.g. Basmati rice, herbal medicines (turmeric, neem etc.).

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