presence or absence of a PCR product

As well as showing the presence or absence of a PCR
product, an agarose gel can also be used to determine the size
of the product. In some instances, agarose gel electrophoresis
alone is sufficient to demonstrate that a mutation is present.
For example, a 250 base pair PCR product containing a
deletion mutation of 10 bases will be readily detected by
agarose gel electrophoresis. Determining the exact position of
the deletion, however, requires additional analysis.