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Biology LibreTexts

20.5: Key Terms

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minoacyl tRNA synthetase
enzyme that “charges” tRNA molecules by catalyzing a bond between the tRNA and a corresponding amino acid
anticodon
three-nucleotide sequence in a tRNA molecule that corresponds to an mRNA codon
central dogma
states that genes specify the sequence of mRNAs, which in turn specify the sequence of proteins
codon
three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation
colinear
in terms of RNA and protein, three “units” of RNA (nucleotides) specify one “unit” of protein (amino acid) in a consecutive fashion
degeneracy
(of the genetic code) describes that a given amino acid can be encoded by more than one nucleotide triplet; the code is degenerate, but not ambiguous
hairpin
structure of RNA when it folds back on itself and forms intramolecular hydrogen bonds between complementary nucleotides
initiator tRNA
in prokaryotes, called tRNAMetf; in eukaryotes, called tRNAi; a tRNA that interacts with a start codon, binds directly to the ribosome P site, and links to a special methionine to begin a polypeptide chain
Kozak’s rules
determines the correct initiation AUG in a eukaryotic mRNA; the following consensus sequence must appear around the AUG: 5’-GCC(purine)CCAUGG-3’; the bolded bases are most important
nonsense codon
one of the three mRNA codons that specifies termination of translation
peptidyl transferase
RNA-based enzyme that is integrated into the 50S ribosomal subunit and catalyzes the formation of peptide bonds
polysome
mRNA molecule simultaneously being translated by many ribosomes all going in the same direction
reading frame
sequence of triplet codons in mRNA that specify a particular protein; a ribosome shift of one or two nucleotides in either direction completely abolishes synthesis of that protein
rho-dependent termination
in prokaryotes, termination of transcription by an interaction between RNA polymerase and the rho protein at a run of G nucleotides on the DNA template
Shine-Dalgarno sequence
(AGGAGG); initiates prokaryotic translation by interacting with rRNA molecules comprising the 30S ribosome
signal sequence
short tail of amino acids that directs a protein to a specific cellular compartment
start codon
AUG (or rarely, GUG) on an mRNA from which translation begins; always specifies methionine
template strand
strand of DNA that specifies the complementary mRNA molecule
transcription bubble
region of locally unwound DNA that allows for transcription of mRNA

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