G?1 G L O S S A R Y Glossary G lo ss ar y Pronounce a- as in ace a/ah ash ch chose e? meet e/eh bet g game ?? ice i hit ks box kw quick ng song o- robe o ox oy boy s say sh shell th thin u? boot u/uh up z zoo ? ? primary accent ? ? secondary accent 5? cap A modi?ed form of guanine nucleotide added onto the 5? end of a pre-mRNA molecule. A site One of a ribosome?s three binding sites for tRNA during translation. The A site holds the tRNA carrying the next amino acid to be added to the polypeptide chain. (A stands for aminoacyl tRNA.) ABC hypothesis A model of ?ower formation identifying three classes of organ identity genes that direct formation of the four types of ?oral organs. abiotic (a??-b??-ot?-ik) Nonliving; referring to the physical and chemical properties of an