Detection of Single-Nucleotide Polymorphisms (SNPs)
of individuals and species are due to mutations that alter the
code. Such single-letter changes result in variable (polymorphic)
polymorphisms or SNPs.
top window shows an 80-nucleotide stretch of DNA from a
of eight Atlantic Cod. Black dots in the upper window flag
at which one individual differs by a single SNP from the
The grey bracket frames an eight-base region with two SNPs,
which the chromatogram data are shown in the lower window.
have the sequence CACATAGG:
individuals BS02 & BS11 share a CT SNP
the third position (CATATAGG)
and individual BS03 has a unique AG SNP at the sixth
of such genetic differences among individuals or species
permits inferences about relationships among individuals in time
(genealogy) and space (phylogeography), and the
history (phylogeny) of species. For example, reconstruction of
pattern of SNP variation shows that individuals BS02 and BS03 are less closely
each other than either is to individual BS01.