RNA Processing, Posttranslational Modifications, and Translation

5' UTR

Untranslated region upstream of the coding sequence; involved in regulation of translation initiation.

Alternative Splicing

Process by which different combinations of exons are joined to produce multiple mRNAs from one gene.

Amino Acid Attachment Site

The 3' end of a tRNA where a specific amino acid is attached.

Aminoacyl-tRNA Synthetase

Enzyme that attaches the correct amino acid to its corresponding tRNA.

Anticodon

Three-nucleotide sequence in tRNA that base pairs with a codon in mRNA.

Branch Site

A specific adenine in the intron critical for splicing in eukaryotic pre-mRNA.

Capping Enzyme

Enzyme that adds a modified guanine (cap) to the 5' end of eukaryotic mRNA.

Cloverleaf Model of tRNA

Structural model of tRNA showing its three stem-loops and acceptor stem

Codon

A three-base sequence in mRNA that specifies an amino acid or stop signal.

Elongation Factors

Proteins that assist the ribosome during the elongation phase of translation.

Exons

Coding regions of a gene that remain in mature mRNA after splicing.

Initiator tRNA

The tRNA carrying methionine (or formylmethionine in prokaryotes) that starts translation.

Initiating Codon (AUG)

The start codon in mRNA that signals the beginning of translation.

Introns

Noncoding sequences in genes that are removed during RNA splicing.

Isoaccepting tRNAs

Different tRNAs that carry the same amino acid but have different anticodons.

Methylated Cap

A 5' cap structure that protects mRNA from degradation and helps with translation initiation.

Methyl Transferase

Enzyme that adds a methyl group to the 5' cap of eukaryotic mRNA.

N-Formylmethionine

The modified methionine used to initiate protein synthesis in prokaryotes.

Nonsense Codon

Also called stop codons (UAA, UAG, UGA); signal the end of translation.

Peptidyl Transferase

The enzymatic activity of the ribosome that forms peptide bonds between amino acids.

Poly-A Polymerase

Enzyme that adds a poly-A tail to the 3' end of eukaryotic mRNA

Poly-A Tail

A stretch of adenine nucleotides added to the 3' end of eukaryotic mRNA to stabilize it.

Polyribosome

A group of ribosomes translating the same mRNA simultaneously.

Primary Transcript

The initial RNA molecule synthesized from DNA; also called pre-mRNA.

Release Factors

Proteins that bind to stop codons and terminate translation.

Ribbon Model

A type of protein structure visualization that emphasizes secondary structures like alpha helices and beta sheets

Ribonuclease

An enzyme that degrades RNA molecules.

Ribosome

Cellular machinery that translates mRNA into protein.

Ribosome Binding Site

Sequence in bacterial mRNA (includes Shine-Dalgarno) where the ribosome binds to initiate translation.

RNA Editing

Post-transcriptional alteration of RNA nucleotide sequence.

Shine-Dalgarno Box

Ribosome binding site in prokaryotic mRNA located upstream of the start codon.

Space-Filling Model

A 3D molecular model that represents the spatial occupation of atoms in a molecule.

Splice Acceptor Site

The 3' end of an intron where splicing occurs.

Splice Donor Site

The 5' end of an intron where splicing begins

Transfer RNA (tRNA)

RNA molecules that bring amino acids to the ribosome during translation.

Trans-splicing

A rare form of splicing where exons from different pre-mRNAs are joined together.

tRNA Wobble

Flexibility in base pairing between the 3rd base of the mRNA codon and the 1st base of the tRNA anticodon.