DNA finger printing, DNA profiling,genetic profiling , DNA typing

DNA finger printing

DNA finger printing, is a method to prepare a picture of sequences of DNA of any individual. Each individual has a unique and different sequence in its DNA.

 

Genes are segments of DNA and DNA are differ in sequence of nitrogen base (nucleotide). Most Segments of DNA (gene) code for a particular protein but all segments of DNA do not code for protein.

Repitetive sequences in DNA finger printing

Some DNA segments are present as non coding  sequences , some are regulatory in function and remaining are known repetitive sequences.

These repetitive sequences are needed for DNA fingerprinting and these sequences are specific from person to person.These nucleotide sequences are termed as variable number of tandem repeat.(VNTR).

DNA fingerprinting distinguishes differences in repetitive sequences or repetitive DNA. Repetitive DNA is a small stretch of DNA in which nucleotide sequences are repeated many times.

Steps involved in DNA fingerprinting

The technique of DNA fingerprinting was developed by Alec Jeffreys. For DNA fingerprinting, DNA is isolated from the blood, hair,semen ,skin and other body parts.DNA fingerprinting involves following steps -

Step -1 DNA is extracted from the cell by using the technique of centrifugation.

Step-2 large numbers of copies of DNA are produced by Polymerase chain reaction (PCR). The production of multiple number of Copies of DNA by using Polymerase chain reaction is called Amplification.

Step -3 DNA is cut into fragments by using restriction enzymes.

Step-4 DNA fragments are separated by gel electrophoresis in a medium of agarose gel. After the separation of DNA fragments, these fragments are visualised under ultraviolet radiation after the staining.

Step-5 The separated DNA sequence is transferred on the membrane of nitrocellulose or nylon membrane.This step is called Southern blotting.

Step-6  The radioactive DNA probes are added in this step. These probes are capable of making hydrogen bonding according to a complementary sequence of separated DNA fragments. This step is known as hybridisation.

Step-7 The separated DNA fragments along with the probe are exposed on X ray film. On x-ray film, a unique pattern of DNA is visualised on x-ray film in the form of Dark and light bands , which look like barcodes. These bands differ from person to person. This whole technique is called Autoradiography.

Advantages of DNA finger printing.

DNA fingerprinting is used to identify the criminals, to settle the paternity dispute, to identify racial groups in terms of biological evolution, to verify the immigrant where he/she is a close relative.