Also known as Identity Matrix. A scoring system in which only
identical characters receive a positive score. (NCBI)
Up-and-Down
the simplest topology for a helical bundle or folded leaf,
in which consecutive helices are adjacent and antiparallel;
it is approximately equivalent to the meander topology of a
beta-sheet. (SCOP)
Uracil
A nitrogenous base normally found in RNA but not DNA; uracil
is capable of forming a base pair with adenine.
See also: base pair, nucleotide
(ORNL)
