are typically inherited in a co-dominant mode: both alleles
expressed as a molecular phenotype.
phenotypes are recognized as sets of bands of particular size in
of an individual heterozygous for two allelic RFLP patterns on
chromosomes, the phenotype includes the patterns from both chromosomes.
In the example, the alternative alleles patterns are a single band of
10Kb, or two bands of 7 & 3 Kb. The heterozygote shows both
patterns, and thus has three bands of 10, 7, and 3 Kb.
may be detected by a variety of methods. In electrophoresis gels (top left), the
bands are DNA stained with ethidium bromide
that fluoresces under ultraviolet light, so that they appear as
red-orange bands against a black background. In Southern
(bottom left), the bands are DNA probed
radioactive labels that
cause the DNA to expose X-ray film, so that they appear as
dark bands against a gray background.