Genetic Engineering Toolbox

DNA fingerprinting - RFLP analysis


Restriction fragment length polymorphisms

Description and Procedure:

This analysis uses many of the techniques found in gene library screening.

1) DNA from white blood cells or other source (hair follicle) is fragmented by a restriction enzyme treatment. These fragments can be amplified by PCR.

2) The sample undergoes electrophoresis which separates the fragments into a pattern of bands (which normally look like broad streaks due to the enormous number of fragments created when an entire genome is fragmented)

3) The fragments are denatured in an alkaline solution and a piece of filter paper laid on top. This Southern blot technique picks up a small sample of DNA from each band creating a mirror image

4) A radioactive probe, designed to highlight a small fraction of the bands, is added to the filter paper and an autoradiograph is taken.

Uses or Function:

RFLP patterns are used to distinguish DNA from different alleles of the same gene. Since these restriction sites are inherited in a Mendelian fashion they can serve as genetic markers for making linkage maps of chromosomes.

The specificity of this technique makes it ideal as an identification tool in forensics (law), evolutionary studies, prenatal diagnosis, and viral detection.