DNA is a 2-
stranded
molecule. Each strand is essentially a
string made up of
letters {
A,C,G,T}, and has an inherent
direction. The two strands go in opposite directions, and have
complementary letters (
A opposite
T,
C opposite
G). The
reverse complement of a
sequence is what appears on the opposite DNA strand; you get it by reversing the sequence and taking complementary letters.
So it's not a notion made-up by bored molecular biologists; it's really an inherent part of nature.
EXAMPLE
The first 60 letters of sequence
AA000008 in
GenBank are:
GGTTTATTTAGAGAATGACATGTGTACACTGTTAAGTGCTGATAGTGGATGCTGCAATTC
The reverse complement is:
GAATTGCAGCATCCACTATCAGCACTTAACAGTGTACACATGTCATTCTCTAAATAAACC