To determine the nucleotide bases A, T, C and G of DNA by sequencing methods is called DNA sequencing. Every organism on the plant earth possesses a complete genetic material. The genetic material contains the full genetic information about the organism. DNA sequencing allows the scientists to use the genetic information in different research purposes like medical research and forensics. Certain biological processes also take place because of the genetic information obtained from the DNA sequencing. DNA sequencing techniques have made possible to do the sequencing of human genome.

Method of DNA sequencing:-
The general method of DNA sequencing is as follows;

1) First the piece of chromosome is taken that contains 50 million or 250 million nucleotide bases. These bases are then converted into smaller pieces.

2) The pieces are used as templates for further processing. These templates produce set of fragments of different lengths.

3) The technique of Agarose DNA gel electrophoresis is used to separate the fragments and keep them in order.

4) Fluorescent dyes are used to separate the set of fragments on the agarose gel and keep them in sequence.

5) The final bases at the end of each strand fragment are identified which when combined together make the short strand which was generated in the first step.

6) When the automated sequencers are used for the analysis of resulting electropherograms, they show four-color chromatogram in which peaks are showing. These peaks represent the four DNA bases.

7) After the visualization of the bases, now computers are use and all the four fragments are combined together to make a long stretch. This long fragment is analyzed for gene coding regions, errors and for many other characteristics.

Benefits of DNA sequencing:-
DNA sequencing enables the scientists to determine genome sequence. Human genome project is the biggest example of DNA sequencing. When the human genome was sequenced back in 2001, many issue rose but now after many year, we can see its impacts on medical and pharmaceutical research. Scientists are now able to identify the genes which are responsible for causing genetic diseases like Alzheimer's disease, Cystic fibrosis, myotonic dystrophy and many other diseases caused by the disability of genes to function properly. Many types of acquired diseases like cancers can also be detected by observing certain genes.

Applications of DNA sequencing:-

Forensics:-
DNA sequencing has been applied in forensics science to identify particular individual because every individual has unique sequence of his/her DNA. It is particularly used to identify the criminals by finding some proof from the crime scene in the form of hair, nail, skin or blood samples. DNA sequencing is also used to determine the paternity of the child. Similarly, it also identifies the endangered and protected species.

Medicine:-
In medical research, DNA sequencing can be used to detect the genes which are associated with some heredity or acquired diseases. Scientists use different techniques of genetic engineering like gene therapy to identify the defected genes and replace them with the healthy ones.

Agriculture:-
DNA sequencing has played vital role in the field of agriculture. The mapping and sequencing of the whole genome of microorganisms has allowed the agriculturists to make them useful for the crops and food plants. For example, specific genes of bacteria have been used in some food plants to increase their resistance against insects and pests and as a result the productivity and nutritional value of the plants also increases. These plants can also fulfill the need of food in poor countries. Similarly, it has been useful in the production of livestock with improved quality of meat and milk.

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