DNA Sequencing

    DNA sequencing is a technique that is employed to discover the nucleotide composition of DNA. It is used for individual gene or whole genome analysis and fundamental genetical research. In the near future DNA sequencing will provide information for targeted medication delivery for oncological and other diseases associated with DNA damage. Human Genome project was launched based on the DNA sequencing methods.

    What is the DNA sequence?

    The DNA consist of the four different nucleotides: Adenine(A), Guanine(G), Thymine(T) and Cytosine(C). They form various combinations that can be translated by the cell to use for its functioning. Discovery of the order in which nucleotides are connected to each other is the target of DNA sequencing.

    What is the scientific basis for DNA sequencing?

     There are many methods used for DNA sequencing. The most recent ones are called next generation DNA sequencing (ChIP-sequencing). They are much chipper and faster than the  previous methods.

    Scientists heat the long double-stranded DNA molecules. That forces strands  to separate and other small sequences of DNA can be bonded with  them. Researchers design those short sequences that serve as a "head" markers.

     Then, enzymes add nucleotides to those short sequences to rebuild the original DNA.  Usually, modified nucleotides are added to the mix (only one modified nucleotide for each  sample) so that they act as a second marker at the "tail" of the sequence. Each type of those modified nucleotides marked with a fluorescent dye of different color.

    When DNA becomes double-stranded again, scientists again heat it and separate strands. They further examine a new DNA, by cutting it with specialized enzymes at the places marked by the designed short sequences and modified nucleotides. Pieces of DNA then separated according to their size in the gel using electrophoresis.

    Markers are designed so that  there will be pieces of DNA that are different just by one nucleotide. Arranged by size, pieces of DNA form a ladder.  By reading the last nucleotides in each step of this ladder, we can discover the sequence of the DNA. The whole process is computerised and relatively quick. Methods can vary by the type and amount of markers used and enzymes involved.

    What are the applications of DNA sequencing?

    The knowledge about the sequence of DNA gives scientists and doctors information about possible diagnosis and treatment of the diseases and makes possible to discover ways for precise, personalised medical treatment and targeted medicine delivery. It can help to determine which DNA sequence is responsible for the particular trait.