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genome analysis a reality. Indeed more advanced methods using nanotechnology

are in development and may provide an even more effective means of DNA

sequencing.

5.11.7 Maxam and Gilbert sequencing

Sanger sequencing is by far the most popular technique for DNA sequencing;

however, an alternative technique developed at the same time may also be used.

The chemical cleavage method of DNA sequencing developed by Maxam and Gilbert

is often used for sequencing small fragments of DNA such as oligonucleotides,

where Sanger sequencing is problematic. A radioactive label is added to either the

30 or the 5^0 ends of a double-stranded DNA sample (Fig. 5.41). The strands are then

Fluorescent chain termination

products migrate down single

lane gel past detector

Laser excitation unit

Diffraction

grating

Charge-coupled

device (CCD)

Computer analysis and

automated base calling

A C G T C G G C T G T G C T G C G

Fig. 5.40Automated fluorescent sequencing detection using single-lane gel and charge-coupled device.

193 5.11 Nucleotide sequencing of DNA