Lesson 6: Translation Key Terms

amino acids

organic molecule containing both an amino group and a carboxyl group

translation

process by which the sequence of nucleotides in an mRNA molecule directs the incorporation of amino acids into protein

genetic code

the set of rules specifying the correspondence between nucleotide triplets (codons) in DNA or RNA and amino acids in proteins

tRNAs

set of small RNA molecules used in protein synthesis as an interface (adaptor) between mRNA and amino acids. Each type of tRNA molecule is covalently linked to a particular amino acid

codon

sequence of three nucleotides in a DNA or mRNA molecule that represents the instruction for incorporation of a specific amino acid into a growing polypeptide chain

open reading frame (ORF)

a continuous nucleotide sequence free from stop codons in at least one of the three reading frames (and thus with the potential to code for protein)

anticodon

sequence of three nucleotides in a transfer RNA (tRNA) molecule that is complementary to a three-nucleotide codon in a messenger RNA (mRNA) molecule

wobble pair

pairing at the third position of the codon and the first position of the anticodon is more flexible. This flexibility allows for certain non-standard base pairings to occur

tRNA chemical modifications

things like methylation, thiolation, deamination, hydroxylation, which can stabilize the tRNA

aminoacyl-tRNA synthethase

enzyme that attaches the correct amino acid to a tRNA molecule to form an aminoacyl-tRNA

tRNA CCA

the universal three-nucleotide sequence (cytosine-cytosine-adenine) found at the 3' end of all mature transfer RNA (tRNA) molecules that serves as the direct attachment site for amino acids

ribosome

particle composed of rRNAs and ribosomal proteins that catalyzes the synthesis of protein using information provided by mRNA

translation initiation

the first and rate-limiting step where the cell assembles the ribosome, messenger RNA (mRNA), and initiator transfer RNA (tRNA) to begin protein synthesis

translation elongation

the middle and longest stage of protein synthesis, where amino acids are added one by one to a growing chain to build a protein

translation termination

final step of protein synthesis where the ribosome releases the completed protein chain from the mRNA instructions

Svedburg unit

used to describe size and shape of a ribsosome, prokaryotic (50S+30S), eukaryotic (60S+40S)

large subunit

the primary catalytic component of the cell's ribosome that links amino acids together to form proteins

small subunit

decodes the genetic message from messenger RNA (mRNA)

peptidyl transferase

a ribozyme located in the large subunit of the ribosome that catalyzes the formation of peptide bonds between amino acids during protein synthesis

initiation factors

specialized proteins that bind to the small ribosomal subunit to help start protein synthesis by assembling the translation machinery at the correct start codon

elongation factors

specialized proteins that help the ribosome extend a growing protein chain during translation

ribozyme

an RNA molecule with catalytic activity

initiator tRNA

special tRNA that initiates translation. It always carries the amino acid methionine, forming the complex Met–tRNAi

(eukaryotic initiation factor) eIF

protein that helps load initiator tRNA on to the ribosome, thus initiating translation

stop codon

a sequence of three nucleotides in DNA or messenger RNA that signals the cell to end protein synthesis

polyribosome

mRNA engaged with multiple ribosomes in the act of translation

start codon

the first three-nucleotide sequence on a messenger RNA (mRNA) molecule that tells the ribosome where to begin making a protein

antibiotics

substance such as penicillin or streptomycin that is toxic to microorganisms

RNA world

hypothesis that early life on Earth was based primarily on RNA molecules that both stored genetic information and catalyzed biochemical reactions

evolution

the change in inherited traits of a living population over successive generations