Recombinant DNA technology has a wide range of application in industries, medical science, and agriculture as “well as molecular biology. Some of its applications are discussed below.
1. Molecular biology:
This technique is used to elucidate molecular events in biological processes like cell differentiation, aging and gene mapping etc.
2. Molecular diagnosis of diseases:
Recombinant DXA technology is used in various ways to diagnose diseases. One way of diagnosis is to involve the construction of probes (short single strand DXA or RXA) with radioactive fluorescent marker. These probes are used to test the DXA of prospective genetic disorder carrier parents.
Their chances of producing afflicted child can be predicted. Xow a days, such probes are also routinely used for identification of infectious agents, for instance, food poisoning Salmonella, pus forming Staphylococcus, hepatitis virus, IIIV etc. Another way is the production of monoclonal antibodies or MAB
3. Monoclonal antibodies
Antibodies are proteins synthesized in blood against antigens. These are a heterogenous mixture of different antibodies in response to different antigens. If specific lymphocytes after isolation and culture invitro, produce a single type of antibody with specificity against a single type of antigen it is known as monoclonal artibody.
The major difficulties with antibody secreting lymphocytes are that they cannot be maintained in culture. But myeloma cells (bone marrow tumour cells due to cancer) grow indefinitely to produce number a large number of clones and also produce same amount of immunoglobins in culture.
Hybrid cells of lymphocytes and myeloma are maintained in culture and are induced with a specific antigen to produce antibodies of that specific antigen. These hybrid cells are called hybridoma and this technique is called hybridoma technique for production of monoclonal antibodies.
(i) Application: Due to the presence of desired immunity (specific antibody), monoclonal antibodies are used in diagnosis of disease, particularly, streptococcal and chlamydial infection.
(ii) Diagnosis of Pregnancy: Pregnancy diagnosis kit contains monoclonal antibodies of hormone excreted only in the urine of pregnant women. When the test sample urine of pregnant women is applied on the strip of pregnancy kit there is antigen-antibody reaction indicated by a colour change. If there is no pregnancy, there will be no reaction and hence no colour hangs.
(iii) Treatment of cancer: In cancer treatment targeted drug delivery is driven by monoclonal antibodies. As a result only cancerous cells receive chemotherapy and the healthy cells are not affected.
4. Gene therapy
Gene therapy means to replace a ‘faulty’ or mutated gene with a healthy gene. Many diseases in humans are caused due to defective genes Xow-a-days intensive investigations are going on for diseases caused by single mutation (damage to a single gene) ranging for sickle cell anaemia to killer diseases such as severe combined Immuno-Deficiency (SCID).
5. DNA Finger Printing
The technique of DNA fingerprinting was developed and established by British geneticist Dr. Alec Jeffreys. Every individual organism is unique in its finger prints. Similarly every individual differs from other in his DNA pattern or design. Finger prints can be altered by surgery but there is no known procedure available to alter the DNA design of an individual. For obtaining the DNA finger prints of an individual, one should look for genes that are highly polymorphic or occur in multiple forms in different individuals. (In other words, genes which are multi allelic in a population)
Principle of DNA finger printing
First of all, for DNA finger printing or profiling or typing short nucleotide sequences having variable number of repeats are identified. These repeats are called variable Number Tandem Repeats or VNTRS. These VNTRS of two individuals may be of same length and same sequence at certain sites of DNA but vary at others. This will be clear if we consider the following example.
Suppose the mother has six VNTRS on one chromosome (two chromatids) and father has four VNTR on the same chromosome (two chromatids). The child will in herit a chromosome with six repeats from mother and its homologous chromosome with four repeats from father. The DNAS/chromosomes samples of father, mother and child collected separately can be compared on gel electrophoresis.
Applications of DNA fingerprinting
This technique can be applied in various fields such as:
(i) In forensic Science to identify the criminals.
(ii) To establish the parentage of a child i.e. to establish the biological father or mother of a child in case of a dispute.
(iii) To identify an ethnic group or to deduce the evolution of a racial group.
6. Production of vaccines
Vaccines are either inactivated (killed) or attenuated pathogens when injected into body of an organism; induces the production of antibodies in the organism against the specific disease (s) caused by the organisms. Recombinant DNA technology has been variously used for commercial production of vaccines such as injectable hepatitis B vacine, malaria vaceine, typhoid vaccine and vaccines against cystic cerosis caused by Taenia soleum. Gene transfer mediated through Ti plasmid to plants can produce edible vaccines.
7. Commercial and pharmaceutical products
Production of human insulin through recombinant DNA technology has revolutionised the management of diabetes. The human insulin gene is cloned and then introduced into E. coli. These engineered E. coli bacteria then grown in cultures produce human insulin. A variety of other commercial products like L-ascorbic acid antibiotics etc are also commercially produced through recombinant DXA technology by genetically engineered organisms.