Chapter 17 Flashcards
The set of triplet code words in DNA (or mRNA) coding for the amino acids of proteins.
genetic code
In a nucleic acid, a sequence of three adjacent nucleotides that codes for a specific amino acid.
codon
A class of RNA molecules (Mr 25,000 to 30,000), each of which combines covalently with a specific amino acid for use in protein synthesis.
Transfer RNA (tRNA)
An aminoacyl ester of a tRNA; the tRNA is charged with an amino acid.
aminoacyl-tRNA:
Enzymes that catalyze synthesis of an aminoacyl-tRNA at the expense of ATP energy.
aminoacyl-tRNA synthetases:
The site in a ribosome where the aminoacyl-tRNA binds.
A site
A specific sequence of three nucleotides in a tRNA, complementary to a codon for an amino acid in an mRNA.
anticodon
The process in which the genetic information present in an mRNA molecule specifies the sequence of amino acids during protein synthesis.
translation
A code in which a single element in one language is specified by more than one element in a second language. The genetic code is degenerate because some amino acids are specified by more than one codon.
degenerate code
A set of multiple codons that specify the same amino acid
codon family
The base at the 5′ end of an anticodon, which pairs loosely and can form mispairs with the base at the 3′ end of the codon.
wobble base
The first position of the anticodon, at the 5′ end, which may contain a wobble base.
wobble position
A hypothesis proposed by Francis Crick in 1966 to describe how some anticodons can recognize more than one codon.
wobble hypothesis
A contiguous, nonoverlapping set of three-nucleotide codons in DNA or RNA.
reading frame
AUG (sometimes GUG or, even more rarely, UUG in bacteria and archaea); codes for the first amino acid in a polypeptide sequence: N-formylmethionine in bacteria; methionine in archaea and eukaryotes. Also called a start codon.
initiation/start codon
UAA, UAG, and UGA; in protein synthesis, these codons signal the termination of a polypeptide chain. Also called stop codons
termination/stop codons
A group of contiguous nonoverlapping nucleotide codons in a DNA or RNA molecule that does not include a termination codon.
open reading frame (ORF):
A single-nucleotide change in a gene that results in an amino acid change in the protein product.
missense mutation
A mutation in a gene that causes no detectable change in the peptide sequence of the gene product.
silent mutation
A point mutation resulting in the exchange of one purine-pyrimidine base pair for another purine-pyrimidine pair. Compare transversion mutation.
transition mutation
A mutation that results in the premature termination of a polypeptide chain.
nonsense mutation
A mutant tRNA that binds to a termination codon but carries an amino acyl residue that can be incorporated into the growing amino acid chain, suppressing the termination signal.
suppressor tRNA
The use of certain degenerate codons more than others to code for a given amino acid.
codon bias
