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GENETIC ENGINEERING

GENETIC ENGINEERING. GENETIC ENGINEERING…. Is a technique to alter the chemistry of genetic material (DNA & RNA). Altered genetic material is introduced into a host organism. This changes the Phenotype of the host organism. STEPS IN PLANT GENETIC ENGG.

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GENETIC ENGINEERING

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  1. GENETIC ENGINEERING

  2. GENETIC ENGINEERING… • Is a technique to alter the chemistry of genetic material (DNA & RNA). • Altered genetic material is introduced into a host organism. • This changes the Phenotype of the host organism.

  3. STEPS IN PLANT GENETIC ENGG. • Identification & isolation of the agronomically important gene. • Isolation of a Plasmid from the bacterium Agrobacterium tumefaciens. • The plant gene of interest is integrated into the DNA of the Plasmid using restriction endonuclease & ligase enzymes. • The recombinant plasmid is introduced into the cultured plant cells. • The plasmid DNA integrates into the plant cell’s chromosomal DNA.

  4. As the plant cells divide, each daughter cell receives a copy of the plasmid DNA and the gene of interest it carries. • These cells give rise to a plantlet. • On transfer into the soil, it grows into a new plant. • This plant expresses the new gene.

  5. GENETICALLY MODIFIED ORGANISMS (GMOs) • Plants, bacteria, fungi and animals, whose genes are altered by manipulation are called Genetically Modified Organisms (GMOs) • GM Plants have been useful in : • Making crops more tolerant to abiotic stresses (Cold, drought, salt, heat) • Reducing reliance on chemical pesticides. (GM plants are pest resistant) • Increased efficiency of mineral usage. • Enhancing nutritional value of food. Eg Vit A enriched rice.

  6. Bt COTTON • The bacterium Bacillus turingenesis is a common soil bacterium. • It produces a toxic insecticidal protein. • This toxin is a crystal protein( Cry) • There are several kinds of Cry proteins, toxic to different groups of insects.

  7. The gene coding for these Cry proteins is called cry gene. • There are a number of cry genes: • cryIAc • cryIIAb • These two produce toxins against cotton boll worms. • cryIAb controls corn borer.

  8. Biotechnologists have been able to isolate the gene responsible for the production of toxin. • Incorporate it into the Agrobacterium Ti plasmid. • This in turn can be introduced into many crop plants. • The new GM Bt cotton is resistant to some caterpillar pests.

  9. PEST RESISTANT PLANTS • Several Nematodes parasitize a wide variety of plants. • A nematode Meloidegyne incognitia infects the roots of tobacco plants and reduces their yield. • RNA interference (RNAi) was used to prevent this infestation. • RNAi is a method of cellular defence in eukaryotes.

  10. RNA Interference • RNAi is a mechanism that inhibits gene expression at the stage of translation or by hindering the transcription of specific genes. • Specific messenger RNA is silenced due to the complementary ds RNA molecule. • The ds RNA binds to the mRNA and prevents its translation.

  11. ds RNA could be from an infection by viruses having RNA genomes or mobile genetic elements called transposons. • Through Agrobacterium vectors, normal copy of genes specific to the nematodes are introduced into the host plant.

  12. The genes of Nematodes are introduced into the host plant. • It produces both sense and antisense RNA in the host cells. • These two RNAs being complementary to each other, formed a double stranded (ds) RNA. • This ds RNA initiated RNA interference and silenced the specific messenger RNA of the nematode.

  13. Thus in the transgenic host, the parasite could not survive expressing the specific interfering RNA. • Thus the tobacco transgenic plant could be saved from the attack of the nematode.

  14. Genetically Engineered Insulin • Insulin is an important life saving drug for diabetic patients. • It is a proteinaceous hormone secreted by the Beta cells of islets of Langerhans. • Each Insulin molecule has 51 amino acids arranged in two chains – A and B chains, bearing 21 and 30 amino acids respectively. • These chains are connected by S-S disulphide bridges

  15. The insulin obtained from pigs has a different amino acid at one point. • The cattle Insulin differs at three points. • Insulin from pig and cattle, sometimes produces allergic reactions. • By using recombinant DNA technology, it is possible to produce human insulin.

  16. In humans Insulin is synthesized as a prohormone which needs o be processed before it becomes functional. • The prohormone contains an extra stretch called C peptide. • This C peptide is removed to form mature Insulin. • On 5th July 1983, an American firm Eli lilly produced the first genetically engineered human insulin by the name Humulin.

  17. Two DNA sequences corresponding to A and B chains were produced. • They were introduced into plasmids of E.coli to produced Insulin chains • A and B chains were produced separately, extracted and combined by creating disulphide bonds. • This formed human Insulin.

  18. Thank you!

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