DNA FINGERPRINTING CLASSIFICATION
It involves the identification of differences in repetitive DNA. Repetitive DNA is repeated many times. It forms the basis of DNA fingerprinting. The technique of DNA fingerprinting was initially developed by Alec Jeffreys to find out markers for inherited diseases.
INTRODUCTION
It involves the identification of differences in repetitive DNA. Repetitive DNA is repeated many times. It forms the basis of DNA fingerprinting. The technique of DNA fingerprinting was initially developed by Alec Jeffreys to find out markers for inherited diseases. Alec Jeffreys in 1985 developed the procedure of genetic analysis and forensic medicine, called DNA fingerprinting. It is individual-specific DNA identification that is made possible by the finding that no two people are likely to have the same number of copies of repetitive DNA sequences of the regions. It is also known as DNA profiling. The chromosomes of every human cell contain scattered through their DNA short, highly repeated 15 nucleotide segments called “mini-satellites” or variable-number Tandem Repeat.
TECHNIQUE OF DNA FINGERPRINTING
Only a small amount of tissues like blood or semen or skin cells or the hair root follicle is needed for DNA fingerprinting. Typically DNA content of about 100,000 cells or about 1 microgram is sufficient. The procedure of DNA fingerprinting involves the following major steps:
(i) DNA is isolated from the cells in a high-speed refrigerated centrifuge.
(ii) If the sample of DNA is very small, DNA can be amplified by Polymerase Chain Reaction
(PCR).
(iii) DNA is then cut up into fragments of different lengths using restriction enzymes.
(iv) The fragments are separated according to size using gel electrophoresis through an agarose
gel. The smaller fragments move faster down the gel than the larger ones.
(v) Double-stranded DNA is then split into single-stranded DNA using alkaline chemicals.
(vi) These separated DNA sequences are transferred to a nylon or nitrocellulose sheet placed over
the gel. This is called “Southern Blotting (after Edward Southern, who first developed this method in 1975).
(vii) The nylon sheet is then immersed in a bath and probes or makers that are radioactive synthetic DNA segments of known sequences are added. The probes target a specific nucleotide sequence that is complementary to VNTR sequences and hybridize them.
(viii) Finally, X-ray film is exposed to the nylon sheet containing radioactive probes. Dark bands develop at the probe sites which resemble the bar codes used by grocery store scanners to identify
(iii) Verify whether a hopeful immigrant is, as he or she claims, really a close relative of already. an established resident.
(iv) Identify racial groups to rewrite biological evolution.
(vi) Gene therapy: The use of bioengineered cells or other biotechnology techniques to treat human genetic disorders is known as gene therapy. Gene therapy is the transfer of normal genes into body cells to correct a genetic defect. It can be used to treat genetic diseases like sickle-cell anemia and Severe Combined Immuno Deficiency (SCID). It (SCID) is caused by a defect in the gene for the enzyme adenosine deaminase (ADA). SCID patients have no functioning T lymphocytes and one. treated with the injections of their white blood cells that have been engineered to carry the normal ADA alleles.
(vii) Transgenics: A gene that has been introduced into a cell or organism is called a transgene (for the transferred gene) to distinguish it from endogenous genes. The animal carrying the introduced foreign gene is said to be a transgenic animal and the possessor called Genetically Modified Organisms (GMOs). Most of the transgenic animals studied to date were produced by microinjection of DNA into fertilized eggs. Prior to microinjection, the eggs are surgically removed from the female parent and fertilized in vitro then DNA is microinjected into the male pronucleus of the fertilized egg through a very fine-tipped glass needle. The integration of injected DNA molecules appears to occur at random sites in the genome.
The first transgenic animal produced was the ‘supermouse by the incorporation of the gene for human growth hormone by Richard Palmiter and Ralph Brinster in 1981.
(viii) Genomics and human genome project: The term genome has been introduced by Winkler in 1920 and genomics is relatively new, coined by Thomas Rodericks in 1986. Genomics is the subdiscipline of genetics devoted to the mapping, sequencing, and functional analysis of genomes. Genomics is subdivided into the following types:
(a) Structural genomics: It is the study of genome structure that deals with the complete nucleotide sequences of the organisms.
(b) Functional genomics: It is the study of genome function which includes transcriptome and proteome. The transcriptome is a complete set of RNAs transcribed from a genome while the proteome is a complete set of proteins encoded by a genome and aims the determination of the structure and function of all the proteins in living organisms. The human genome project, sometimes called “biology’s moon
Prospects and implications of the human genome :
(1) The genome project is being compared to the discovery of antibiotics.
(2) Efforts are in progress to determine genes that will revert cancerous cells to normal.
(3) human genome sequencing not only holds promise for healthier living. It also holds the prospects of a vast database of knowledge about designer drugs. genetically modified diets and finally our genetic identity.
IMPORTANT TIPS
Palindromic DNA is a segment of DNA in which the base pair sequence reads the same in both directions from a point of symmetry. Western blotting is the technique used to detect specific proteins. Northern blotting is the technique used to blot transfer RNAs. Recombinant DNA is also called chimeric DNA.Eli Lily (an American company) in 1983 produced genetically engineered insulin called humulin with the help of an E. coli plasmid clone. DNA footprinting: It determines the location and lengths of binding sites of various proteins that bind to DNA. Hargovind Khorana is associated with genetic engineering. He synthesized gene’ artificially in a test tube in 1969. Polymerase Chain Reaction (PCR) was developed by Kary Mullis in 1983 and got a Nobel prize for chemistry. The southern blotting technique is used for separating DNA fragments and identification of cloned genes. Gel electrophoresis and autoradiography are employed in nucleic and blotting. Delayed ripening is possible by reducing the amount of cell wall degrading enzyme ‘Polygalacturonase’ responsible for fruit softening.
FAQs
- Are fingerprints identify the DNA?
Ans. yes, even a single fingerprint classifies the DNA.
