Sequencing Dna
A gene is a segment of DNA that carries the information needed by the cell to construct a protein. Which protein that is, when it is made, and how damage to it can give rise to genetic disease all depend on the gene's sequence. In other words, they depend on how the building blocks of DNA, the nucleotides A, C, G, and T (adenine, cytosine, guanine, and thymine) are ordered along the DNA strand. For example, part of a gene may contain the base sequence TGGCAC, while part of another gene may contain the base sequence TCACGG. Knowing a gene's base sequence can lead toisolation of its protein product, show how individuals are related, or point the way to a cure for those people carrying it in its damaged form.
Overview
In 1977 two methods for sequencing DNA were introduced. One method, referred to as Maxam-Gilbert sequencing, after the two scientists at Harvard University who developed the technique, uses different chemicals to break radioactively labeled DNA at specific base positions. The other approach, developed by Frederick Sanger in England and called the chain termination method (also called the Sanger method), uses a DNA synthesis reaction with special forms of the four nucleotides that, when added to a DNA chain, stop (terminate) further chain growth.
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