amino acid phenylalanine (Phe)--is depicted in various ways. (A) The cloverleaf structure, a convention used to show the complementary base-pairing (red lines) that creates the double-helical regions of the molecule. The anticodon is the sequence of three nucleotides that base-pairs with a codon in mRNA. The amino acid matching the codon/anticodon pair is attached at the 3?end of the tRNA. tRNAs contain some unusual bases, which are produced by chemical modification after the tRNA has been synthesised. The bases denoted psi (for pseudouridine) and D (for dihydrouridine) are derived from uracil. (B and C) Views of the actual L-shaped molecule, based on x-ray diffraction analysis. (D) The linear nucleotide sequence of the molecule, colour-coded to match A, B, and C
