Protein Synthesis

Gene

DNA segment that codes for a specific protein or trait.

mRNA

Carries genetic code from DNA to ribosomes.

tRNA

Brings amino acids to the ribosome during translation.

rRNA

Structural component of ribosomes.

Transcription

Process of copying DNA into RNA.

Translation 

Process of assembling proteins based on mRNA sequence.

RNA Polymerase

Enzyme that synthesizes RNA from a DNA template.

Promoter region

DNA sequence where RNA polymerase binds to start transcription.

Post-transcriptional modifications

Changes to mRNA before leaving the nucleus (splicing, capping, tailing).

Primary mRNA

Initial RNA transcript before processing.

Mature mRNA

Processed mRNA ready for translation.

5’ guanine cap 

Protective modification added to mRNA’s 5’ end.

3’ poly-A tail 

Chain of adenine nucleotides added to mRNA’s 3’ end.

Introns

Noncoding regions removed from pre-mRNA.

Exons

Coding sequences that remain in mature mRNA.

Splicing

Process of removing introns and joining exons.

Spliceosome enzyme

Complex responsible for splicing mRNA.

Degeneracy of the code

Multiple codons can specify the same amino acid.

Codon

Three-base sequence on mRNA that codes for an amino acid.

Anticodon

Three-base sequence on tRNA complementary to mRNA codon.

Amino acid

Building block of proteins.

Start codon

Signals beginning of translation (AUG).

Stop codon

Signals end of translation (UAA, UAG, UGA).

Ribosomes

Site of protein synthesis.

Nucleolus

Organelle where rRNA is produced.

Ribosomal subunits

Large and small components of ribosomes that assemble during translation.

Ribosomal binding sites 

Locations on ribosome for tRNA (A, P, E sites).

Polyribosome/Polysome

Several ribosomes translating one mRNA simultaneously.

Initiation

First stage of translation when mRNA and tRNA assemble on the ribosome.

Elongation

Addition of amino acids to the growing polypeptide chain.

Termination 

Final step of translation when a stop codon is reached.

Initiator tRNA 

tRNA carrying methionine that starts translation.

P site

Holds tRNA carrying the growing polypeptide chain.

A site

Holds incoming tRNA with an amino acid.

E site

Exit site for empty tRNA.

Peptide bond

Bond between amino acids in a protein.

Release factor

Protein that ends translation by releasing the polypeptide.

Post-translational modifications

Changes to proteins after translation (folding, cleavage, etc.).

Mature protein

Final, functional form of a protein.