DNA sequencing is the process of determining the exact order of the bases A, T, C and G in a piece of DNA. In essence, the DNA is used as a template to generate a set of fragments that differ in length from each other by a single base. The fragments are then separated by size, and the bases at the end are identified, recreating the original sequence of the DNA.
DNA is basically a long molecule that contains coded instructions for the cells. Everything the cells do is coded somehow in DNA - which cells should grow and when, which cells should die and when, which cells should make hair and what color it should be.Most DNA sequencing is carried out using the chain termination method. This involves the synthesis of new DNA strands on a single stranded template and the random incorporation of chain-terminating nucleotide analogues.
The DNA to be sequenced is provided in single-stranded form. This acts as a template upon which a new DNA strand is synthesised. DNA synthesis requires a supply of the four nucleotides (the building blocks of DNA), the enzyme DNA polymerase and a primer (a short sequence annealed to the template which initiates the new DNA strand). The nucleotides added to the growing DNA strand are complementary to those in the template strand.
The most obvious application of DNA sequencing technology is the accurate sequencing of genes and genomes. Only about 500-800 bases can be sequenced in one experiment so larger DNA molecules, including whole genomes, must be broken into smaller fragments before sequencing and then reassembled by searching for overlaps. Accuracy is achieved by sequencing each template several times.
Efficient DNA sequencing of the genomes of individual species and organisms is a critical task for the advancement of biological sciences, medicine and agriculture. Advances in modern sequencing methods are needed to meet the challenge of sequencing such megabase to gigabase quantities of DNA. Two possible strategies for DNA sequencing exist.
DNA is basically a long molecule that contains coded instructions for the cells. Everything the cells do is coded somehow in DNA - which cells should grow and when, which cells should die and when, which cells should make hair and what color it should be.Most DNA sequencing is carried out using the chain termination method. This involves the synthesis of new DNA strands on a single stranded template and the random incorporation of chain-terminating nucleotide analogues.
The DNA to be sequenced is provided in single-stranded form. This acts as a template upon which a new DNA strand is synthesised. DNA synthesis requires a supply of the four nucleotides (the building blocks of DNA), the enzyme DNA polymerase and a primer (a short sequence annealed to the template which initiates the new DNA strand). The nucleotides added to the growing DNA strand are complementary to those in the template strand.
The most obvious application of DNA sequencing technology is the accurate sequencing of genes and genomes. Only about 500-800 bases can be sequenced in one experiment so larger DNA molecules, including whole genomes, must be broken into smaller fragments before sequencing and then reassembled by searching for overlaps. Accuracy is achieved by sequencing each template several times.
Efficient DNA sequencing of the genomes of individual species and organisms is a critical task for the advancement of biological sciences, medicine and agriculture. Advances in modern sequencing methods are needed to meet the challenge of sequencing such megabase to gigabase quantities of DNA. Two possible strategies for DNA sequencing exist.
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