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Biotechnology Principles and Processes Class 12 Notes Biology Chapter 9

Recombinant DNA Technology

  • Definition: Genetic engineering, a kind of biotechnology, is the latest branch in applied genetics dealing the alteration of the genetic makeup of cells by deliberate and artificial means. Genetic engineering involves transfer or replacement of genes, so also known as recombination DNA technology or gene splicing.

Recombinant DNA TechnologyRecombinant DNA TechnologyTools of genetic engineering:

  • Two enzymes used in genetic engineering are restriction endonuclease and ligases.
  • R.E. is used to cut the plasmid as well as the foreign DNA molecules of specific points while ligase is used to seal gaps or to join bits of DNA.
  • The ability to clone and sequence essentially any gene or other DNA sequence of interest from any species depends on a special class of enzymes called restriction endonucleases.
  • Restriction endonucleases are also called as molecular scissors or ‘chemical scalpels’.
  • Restriction endonucleases cleave DNA molecules only at specific nucleotide sequence called restriction sites.
  • The first restriction enzyme identified from a bacterial strain is designated I, the second II and so on, thus, restriction endonuclease EcoRI is produced by Escherichia coli strain RY 13.
  • Restriction enzyme called EcoRI recognizes the sequenceBiotechnology Principles and Processes Class 12 Notes Biology Chapter 9
  • It then cleaves the DNA between G and A on both strands. Restriction nucleases make staggered cuts; that is, they cleave the two strands of a double helix at different joints and blunt ended fragments; that is, they cut both strands at same place.

Steps of Recombinant DNA Technology:

  • Isolating a useful DNA segment from the donor organism.
  • Splicing it into a suitable vector under conditions to ensure that each vector receives no more than one DNA fragment.
  • Producing of multiple copies of his recombinant DNA.
  • Inserting this altered DNA into a recipient organism.
  • Screening of the transformed cells.

Vectors

Vector in genetic engineering is usually a DNA segment used as a carrier for transferring selected DNA into living cells. These are as follows:
PlasmidPlasmid1. Plasmid: Plasmid is extra chromosomal, closed circular double stranded molecules of DNA present in most eukaryotes. All plasmid carry replicons pieces of DNA that have the genetic information required to replicate. Plasmid pBR 322 was one of the first widely used cloning vectors, it contain both ampicillin and tetracycline resistance genes.
2. Phage: It is constructed from the phage l chromosomes and acts as bacteriophage cloning vectors.
3. Cosmid: The hybrids between plasmid and the phage l chromosome give rise to cosmid vectors.
CosmidCosmid4. Beside all these there are artificial chromosomes like

  • BACs (Bacterial Artificial chromosomes)
  • YACs (Yeast Artificial chromosomes)
    (iii) MACs (Mammalian Artificial chromosomes) are very efficient vectors for eukaryotic gene transfers.

Application of recombinant DNA technology:
The technique of recombinant DNA can be employed in the following ways.

  • It can be used to elucidate molecular events in the biological process such as cellular differentiation and ageing. The same can be used for making gene maps with precision.
  • In biochemical and pharmaceutical industry, by engineering genes, useful chemical compounds can be produced cheaply and efficiently which is shown in table.

Applications of recombinant DNA products

Medically useful recombinant products

Applications

Human insulin

Treatment of insulin-dependent diabetes

Human growth hormone

Replacement of missing hormone in short stature people

Calcitonin

Treatment of rickets

Chronic gonadotropin

Treatment of infertility

Blood clotting factor VIII/IX

Replacement of clotting factor missing in patients with Haemophilia A/B

Tissue plasminogen activator

Dissolving blood clots after heart attacks and strokes

Erythropoitin

Stimulation of the formation of erythrocytes (RBCs) for patients suffering from anaemia during kidney dialysis or side effects of AIDS patients treated by drugs

Platelet derived growth factor

Stimulation of wound healing

Interferon

Treatment of pathogenic viral infections, cancer

Interleukins

Enhancement of action of immune system

Vaccines

Prevention of infectious diseases such as hepatitis B, herpes, influenza, pertussis, meningitis, etc.



Cloning

Cloning is the process of producing many identical organisms or clones. In this process nucleus of ovum (n) is removed and replaced by nucleus of diploid cell of same organism. Now the egg with 2n nucleus is transferred to the uterus of mother to have normal pregnancy and delivers clone of itself.
Examples of organism cloning

  • Cloning of sheep was done by Dr. Ian Wilmut (1995) of Roslin Institute, Edinberg U.K. and normal healthy lamb (DOLLY) was born in Feb, 1996. This lamb was exactly similar to her mother.
  • The first cloned calves George and Charlie were born in January 1998.
  • ANDI was the world’s first genetically altered primate produced by inserting a jelly fish gene into the embryo of a rhesus monkey.
  • Scientist at Scotland cloned POLLY and MOLLY. Unlike Dolly, polly and molly were transgenic (they carried human protein gene) polly and molly were born in july 1997.
  • Brigitte Boissliar, a 46-year old french chemist announced the creation of the world’s first cloned human boby nicknamed “Eve” (December 2002).

Polymerase chain reaction (PCR):

  • It was developed by Kary Mullis in 1983 and won Nobel Prize in 1993.
  • PCR is a method for amplifying a specific piece of DNA molecule without the requirement for time-consuming cloning procedure.
  • This process require Target DNA, a heat stable DNA polymerase, which work at optimum temperature of 70°C usually Taq DNA and four types of nucleotides with small single stranded strands of DNA of about 20 nucleotide called primers, produce multiple copy of desired DNA.
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FAQs on Biotechnology Principles and Processes Class 12 Notes Biology Chapter 9

1. What is recombinant DNA technology and how is it used in biotechnology?
Ans. Recombinant DNA technology involves the manipulation of DNA molecules from different sources to create new combinations of genetic material. It is used in biotechnology to produce genetically modified organisms (GMOs), develop new medicines, and improve crop yields.
2. What are vectors in the context of recombinant DNA technology?
Ans. Vectors are DNA molecules used to transport foreign DNA into host cells during genetic engineering experiments. They act as carriers to deliver the desired DNA into the target organism, allowing it to be replicated and expressed.
3. How does cloning work in the context of recombinant DNA technology?
Ans. Cloning in recombinant DNA technology involves the production of genetically identical copies of a DNA sequence, gene, or an entire organism. This is achieved by inserting the desired DNA into a vector, which is then introduced into host cells. The host cells replicate and express the inserted DNA, resulting in the production of multiple identical copies.
4. What are some applications of recombinant DNA technology?
Ans. Recombinant DNA technology has a wide range of applications, including the production of therapeutic proteins such as insulin and growth hormones, development of genetically modified crops with improved traits, gene therapy for treating genetic disorders, and the production of vaccines.
5. What are some ethical considerations associated with the use of recombinant DNA technology?
Ans. The use of recombinant DNA technology raises ethical concerns related to the potential risks and impacts on the environment, biodiversity, and human health. It also raises questions about the ownership and control of genetically modified organisms and the potential for unintended consequences in altering the genetic makeup of organisms.
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