Detection of a point mutation by oligonucleotides

Short segments of DNA (oligonucleotides) are
used to determine whether there is a mutation
in a segment of DNA (1, normal DNA; 2, mutation
from G to A). An oligonucleotide is a synthetically
produced DNA segment about 20 nucleotides
long; its sequence is complementary
to a corresponding segment of the investigated
gene. It hybridizes completely with its complementary
segment (3). If a mutation, here
from G to A (1), is located in this region, hybridization
will not be perfect at this site (mismatch)
(4). On the other hand, an oligonucleotide
that is complementary to the DNA segment
with the mutation will hybridize
completely (allele-specific oligonucleotide,
ASO) (5). This hybridizes incompletely with the
normal DNA (6). By parallel use of both nucleotides,
mutant and nonmutant DNA can be
differentiated. The test results (7) show the hybridization
of mutated DNA and of control DNA
with the allele-specific oligonucleotides (ASO 1
for the control, ASO 2 for the mutation).