Comprehensive Guide to Translation and the Genetic Code

Comprehensive vocabulary flashcards covering the components, mechanisms, and stages of translation, the genetic code, and elongation factors described in the lecture.

Genetic Code

The codon code consisting of $64$ codons used by ribosomes to create a polypeptide chain using messenger RNA as a template.

Peptide Bond

A covalent bond formed by a condensation or dehydration synthesis reaction between the carboxyl terminus of one amino acid and the amine terminus of another, linking amino acids together into a primary structure.

Codon

A set of three nucleotides in messenger RNA written in the $5'$ to $3'$ direction that encodes a specific amino acid or a stop signal.

Sense Codons

The $61$ codons in the genetic code that specify and encode for amino acids.

Nonsense Codons

The $3$ codons (stop codons: UAA, UAG, and UGA) that do not encode any amino acid, signaling the ribosome to terminate translation.

Degeneracy of the Genetic Code

The feature of the genetic code where a single amino acid can be specified by more than one codon, accounting for $64$ codons encoding only $20$ biological amino acids.

Synonymous Codons

Different codons that specify the exact same amino acid (such as the six different codons that encode leucine).

Isoaccepting tRNAs

Different tRNA molecules that accept and carry the same amino acid but possess different anticodons recognizing different codons.

Wobble Hypothesis

The principle stating that standard Watson-Crick base-pairing rules are relaxed at the third position of an mRNA codon, enabling a single tRNA anticodon to pair with more than one codon.

Reading Frame

The specific non-overlapping grouping of nucleotides into sets of three codons read by the ribosome; every mRNA transcript contains three potential reading frames.

Mycoplasma capricolum

A bacterial species that represents an exception to the universal genetic code because its UGA codon encodes the amino acid tryptophan rather than functioning as a nonsense (stop) codon.

Aminoacyl-tRNA Synthetase

An enzyme with two active sites that attaches an amino acid to its corresponding tRNA in a two-step, ATP-dependent charging reaction; there are $20$ different synthetases in the cell.

tRNA Acceptor Arm

The site on the $3'$ end of a tRNA molecule featuring a CCA motif, where the carboxyl group of an amino acid is covalently linked to the $2'$ or $3'$ hydroxyl group of the terminal adenine nucleotide.

Coupled Transcription and Translation

The simultaneous occurrence of transcription and translation on an mRNA transcript, occurring uniquely in prokaryotes because they lack a nucleus to separate these processes and do not undergo RNA processing.

Shine-Dalgarno Sequence

A consensus sequence located upstream of the AUG start codon in bacterial mRNA that is recognized by complementary base pairing with the $16\text{S}$ rRNA of the small ribosomal subunit to initiate translation.

Kozak Sequence

A sequence surrounding the start codon in eukaryotic mRNA that facilitates the identification of the AUG start codon by the small ribosomal subunit.

N-formylmethionine (fMet)

A specialized form of methionine carried by the initiator tRNA in bacteria that binds to the AUG start codon alongside the small ribosomal subunit and initiation factors during translation initiation.

Aminoacyl (A) Site

The acceptor pocket within the ribosome where an incoming charged tRNA enters and pairs its anticodon with the complementary mRNA codon.

Peptidyl (P) Site

The ribosomal pocket where peptide bond formation occurs between the growing polypeptide chain and the incoming amino acid situated in the A site.

Exit (E) Site

The ribosomal pocket into which an uncharged (empty) tRNA moves after peptide bond formation before being released into the cytoplasm.

EF-Tu (EFTU)

An elongation factor that complexes with GTP to bind and stabilize the incoming charged tRNA into the ribosomal A site, hydrolyzing GTP to GDP upon entry.

EF-Ts (EFTS)

An elongation factor that regenerates the active EF-Tu complex by facilitating the exchange or recycling of GDP back into GTP.

EF-G (EFG)

An elongation factor that utilizes GTP hydrolysis to power the translocation of the ribosome down the mRNA by three nucleotides (one codon).

Release Factors

Proteins that enter the ribosomal A site upon recognition of a stop codon (UAA, UAG, or UGA) to stimulate GTP hydrolysis, terminate translation, and release the completed polypeptide chain.