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.

Read more about the Restriction enzyme

• 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).

Read more about the Polymerase chain reaction

• 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.

Read more about the Gel Electrophoresis 

• 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.