RNA polymerase The enzyme that directs the link-
ing of ribonucleotides during transcription.
RNA See RIBONUCLEIC ACID.
RNA processing Synthesis of messenger RNA
(mRNA) in a eukaryotic cell involves numerous succes-
sive steps: transcription initiation and elongation; RNA
processing reactions, such as capping (modification of
the 5’-ends of eukaryotic mRNAs), splicing (removing
introns, “junk” DNA), and polyadenylation (modifica-
tion of the 3’-ends of eukaryotic mRNA); and finally
termination of transcription.RNA splicing The process of removing introns, the
noncoding regions of eukaryotic genes that are tran-
scribed into mRNA.
See alsoRNA PROCESSING.Robbins, Frederick Chapman(1916– ) American
Pediatrician Frederick Chapman Robbins was born in
Auburn, Alabama, on August 25, 1916, to William J.Robbins, Frederick Chapman 297Enlarged view of mouthparts of an American dog tick, Dermacentor variabilis,magnified 779×.Ticks are of the class Arachnida, as are
spiders and mites. D. variabilisis a known carrier of Rocky Mountain spotted fever caused by the bacterium Rickettsia rickettsii.
(Courtesy of Janice Carr, Centers for Disease Control and Prevention)