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