Ch. 20 Restriction Enzymes

GeneralBiologyOnline

Index to All Chapters

General
---------Biology-----------------------------------------------------
------------------Online---------------------------------------------------------------------------------- Ch. 20 DNA Technology

DNA Fingerprinting

The following sequence illustrates

how restriction enzymes cut DNA into "fragments,"
how a lab would do this in a test tube, and
how electrophoresis is used to separate the fragments into groups of same size fragments, i.e. RFLP's (restriction fragment length polymorphism's).

Assume you had isolated a fragment of DNA from under the fingernails of a murder victim. First you would need to make lots of copies of the DNA using the polymerase chain reaction (PCR). The PCR is not shown here, but is involves all the chemicals necessary to replicate a cells genome during the S Phase of the cell cycle. Assume the 10 strands below were produced by PCR, and then cut by a restriction enzyme in a test tube.

The banding pattern on the gel is the RFLP, "restriction fragment length polymorphism." Each band represents a collection of fragments that are all the same length. Poly = many and morp = pattern, shape or structure. Just as the coding sequence of your DNA is unique, the RFLP pattern is unique and can be used as a "fingerprint."

contents