Showing posts with label DNA Sequencing. Show all posts
Showing posts with label DNA Sequencing. Show all posts

DNA Sequencing

Posted by bhavin | Posted in | Posted on 10:28 PM

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DNA Sequencing is the process that determines the exact order of the three billion chemical building blocks known as bases and abbreviated as A, T, C and G. These three billion building blocks are responsible to make up the DNA of the twenty-four different human chromosomes. DNA Sequencing maps are greatly used by the scientists for exploring the human biology as well as many other complex phenomenons related to our body.

The exact order of the bases A, T, C and G are determined in a piece of DNA through DNA Sequencing. In the core, DNA is used as a template for generating a set of fragments differing in length from each other by a single base. These fragments are then separated by size and the bases are recognized at the end, recreating the original sequence of DNA.

The most frequently used method for DNA Sequencing is the dideoxy method or the chain termination method. This method was developed by Fred Sanger. The basics involved in this method is the use of adapted bases known as dideoxy bases. When the DNA piece is replicated and the dideoxy base is integrated in a new chain, the replication reaction stops immediately.

Most of the DNA Sequencing is done by this chain termination method. In this method, a new DNA strand is synthesized on a single stranded template and the chain terminating nucleotide analogues are randomly incorporated. This method leads to the production of a set of DNA molecules that differs in length by a nucleotide. The last base in every molecule can be identified easily due to its unique label. Separation of the DNA molecules as per to their sizes, locates them in a correct order to read off the sequence.

The DNA Sequencing method forms the basis of the automated cycle sequencing reactions. In these reactions, fluorescent dyes are added and a laser, inside the automated DNA Sequencing machine is used for analyzing the DNA fragments that are produced in the process. For sequencing a piece of DNA, you require a short DNA “primer” that is complimentary to the DNA that you wish to sequence, a template DNA i.e. the DNA that you want to sequence, an enzyme known as DNA polymerase and four nucleotides.

DNA Sequencing is a very useful method. The most foreseen application of DNA Sequencing is seen in accurate sequencing of the genomes and genes in your body. Only up to 500-800 bases can be sequenced in one demonstration. So, obviously, the larger DNA molecules along with the genomes should be broken down in small fragments before sequencing them. You will get accuracy only when you sequence each template for a number of times. Low fidelity single pass sequencing is very useful for quick accumulation of the sequence data. Another application where DNA Sequencing is seen is in resequencing the same DNA molecule again and again. This is very important, for instance, in typing of the single nucleotide polymorphisms.

DNA Sequencing is the center of Human Genome Project and it promises to revolutionalize the Biomedical Sciences as well as the treatment of the human disease.

DNA Sequencing

Posted by bhavin | Posted in , , | Posted on 11:15 AM

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DNA Sequencing is a process to determine the precise order of the billions of chemical blocks known as bases. These bases are adenine, thymine, cytosine and guanine and they are abbreviated as A, T, C, and G respectively. They constitute the DNA of the twenty-four different chromosomes present in the human beings. DNA Sequencing contains the heritable genetic data in mitochondria, nuclei, chloroplasts and plasmids. These are responsible to form the base of the developmental programs in all the living organisms.

Thus, determination of the DNA Sequencing is of great help in studying the fundamental biological processes in basic research and in the applied fields like forensic and diagnostic research.  DNA Sequencing has initiated significant acceleration in biological discovery and research. The advent of modern technologies has attained rapid sequencing speed that is influential in the sequencing the large-scale human genome in the Human Genome Project.

For sequencing a piece of DNA, you will require the following: a DNA template containing the DNA that you want to sequence, DNA polymerase enzyme, DNA primer complimentary to the DNA that is being sequenced and four nucleotides. The most common method used for DNA Sequencing is the chain termination method. In this method, modified bases known as dideoxy bases are used. Replication of the DNA piece and incorporation of a dideoxy base in the new chain ceases the replication reaction.

The DNA that is to be sequenced is taken in a single strand form. This single strand acts as template on which the synthesis of a new DNA strand will take place. A nucleotide is included in each reaction, which cannot be extended. This nucleotide acts as a chain terminator. Four reactions, all containing the similar primer and template are set up. The process of incorporation of a new DNA strand takes place randomly as only a small amount of chain terminator is contained in the reaction. Thus, a collection of fragments is generated in each reaction, but all the DNA strands will end up with the same bases (A, C, T or G).

Most of the DNA Sequencing is done by the chain termination method. In the chain termination, method the synthesis of a new DNA strand takes place on a single stranded template. This method generates a set of the DNA molecules that differ in length from one another only by one nucleotide. You can easily recognize the last base in each molecule depending on the size that positions them in an exact order in order to read off the sequence easily.

DNA Sequencing technology is used widely in sequencing the genes and genomes precisely. The more number of times the template is being sequenced, the more accuracy will be achieved. This single-pass and low-fidelity sequencing is of great help in accumulating the sequence information rapidly as well as accurately. Another application where DNA Sequencing is of great use is in resequencing the same type of DNA molecule repeatedly. This is essential in the typing of the single nucleotide polymorphisms.

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