DNA Fingerprinting
DNA fingerprinting involves identifying differences in some specific regions in DNA called repetitive DNA because, in these sequences, a small stretch of DNA is repeated many times. Alec Jeffrey who initially developed this technique used satellite DNA as the basis of DNA fingerprinting that shows a very high degree of polymorphism. It was called Variable Number Tandem Repeats. (VNTR). Its steps are;
- Isolation of DNA.
- Digestion of DNA by restriction endonucleases.
- Separation of DNA fragments by gel electrophoresis.
- Transferring (blotting) separated DNA fragments to synthetic membranes, such as nitrocellulose or nylon.
- Double-stranded DNA is made single-stranded by opening the bonds.
- Hybridization is done using a labeled VNTR probe.
- Detection of hybridized DNA fragments After hybridization with the VNTR probe the autoradiogram gives many bands of different sizes
- These bands give a characteristic pattern for an individual DNA. It differs from individual to individual.
The basis of DNA fingerprinting is;
- Repetitive DNA: DNA carries some non-coding repeated sequences.
- Satellite DNA: These are highly-repeated short sequences in the repetitive DNA.
Applications of DNA Fingerprinting
- Test of paternity.
- Identification of the criminals in unknown cases based on tissue samples e.g. rape, murder, etc.
- Population diversity determination or phylogenic status of animals
- Determination of genetic diseases.
Molecular Basis of Inheritance Notes Class 12
CBSE Class 12 Molecular Basis of Inheritance: Inheritance is transmitted by certain molecules that Mendel termed as ‘factors’, but their nature was discovered later with the development of various scientific techniques. The molecules which govern the inheritance are called genes and it is of two types; Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA). In all organisms except viruses, DNA acts as the genetic material whereas RNA acts as the messenger molecule, however in some viruses RNA functions as the genetic material. It is because DNA is a more stable molecule as compared to RNA and hence, it evolved as the genetic material of almost all the organisms.