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Biology - DNA sequencing

DNA sequencing

DNA sequencing is a process by which the order of nucleotides [1] (bases)
in a segment of DNA is worked out. This then provides information about
what amino acids [2] the segment codes for.

The sample of DNA is prepared by cutting into fragments using restriction
enzymes [3] that target particular bases. The ends of the fragments are
labelled with radio-active nucleotide markers. The fragments of different
lengths are separated by gel electrophoresis, [4] using 4 lanes into which
identical samples of DNA fragments are placed.

The DNA of a lane is labelled with a particular radioactive nucleotide
marker (C, G, A or T). By looking at the 4 lanes the sequence of
nucleotides in the DNA can be read (from negative end to positive end of
the gel). The amino-acid sequence can be worked out by following successive
steps:

* convert the gel sequence of bases [5] into the template strand of DNA;

* work out the mRNA sequence from the template strand;

* work out the amino-acid sequence of the polypeptide [6] chain using the
mRNA table.

Watch the video that shows a DNA sequencing machine in a DNA testing
laboratory.

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Links:
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[1] http://alison.com/#
[2] http://alison.com/#
[3] http://alison.com/#
[4] http://alison.com/#
[5] http://alison.com/#
[6] http://alison.com/#