Gene sequencing means finding out the order of bases in a gene.
How fluorescently labelled probes are used:
1) A sample of DNA is digested into fragments using restriction endonuclease enzymes and separated using electrophoresis.
2) The separated DNA fragments are then transferred to a nylon membrane and incubated with a fluorescently labelled DNA probe. If the gene if present, the DNA probe will hybridise (bind) to it.
3) The membrane is then exposed to UV light and if the gene is present there will be a flourescent band.
Once youv'e located a gene DNA sequencing can be used. Restriction enzymes are used to to cut genes into smaller sections. (because most genes are too long to be sequenced at one go).
DNA base sequencing: can be used to determine the order of bases in a section of DNA- so it can be used to sequence fragments of genes. It can be carried out by the chain termination method.