Transcription leads to the production of hnRNA (heterogeneous nuclear RNA), which primarily consists of pre-mRNA and must go through processing and modification to form mRNA and leave the nucleus.

The other three choices, mRNA (messenger RNA), tRNA (transfer RNA), and rRNA (ribosomal RNA), all play active roles in the process of translation. mRNA serves as the codon template. tRNA matches anticodons to mRNA and carries amino acids. rRNA forms a large part of the ribosome structure and plays a functional role as the site of translation.

Translation is the process of making a polypeptide chain from an mRNA template. No new molecules of RNA or DNA are synthesized during this process. tRNA is used to bring amino acids to the ribosome, binding an anticodon to the exposed codon of mRNA. The amino acid is then released from the tRNA and added to the growing chain of amino acids attached to the ribosome. When the ribosome reaches a stop codon, it releases the mRNA strand and amino acid sequence. The amino acid sequence is the final result of translation, and is known as a polypeptide.

Polypeptides can then undergo folding to become functional proteins. All enzymes are proteins, but not all proteins go on to become enzymes; some serve other functions.

The mRNA strand is translated into a protein using triplets, or three nucleotides. Each triplet is called a codon. Messenger or mRNA codons bind to complementary anti-codons on tRNA molecules, which carry the corresponding amino acids.

The wobble position refers to the ability of the third position nucleotide of the codon and first position nucleotide of the anticodon tRNA sequence (when reading in a 5’ to 3’ direction) to exhibit non-standard base pairing. This allows fewer tRNA molecules to exist because a tRNA molecule is able to bind to more than one codon, which increases efficiency.

During the elongation stage of translation, GTP is used to provide the energy to translocate a tRNA molecule from the A-site to the P-site. GTP is also required to move the ribosome down the mRNA strand to the next codon.

In translation, stop codons within the mRNA strand signal the termination of the protein sequence to be translated. The stop codon nucleotide triplets are UAG, UGA, and UAA. Stop codons do not bind to an anticodon within a tRNA molecule, but rather to release factors. Release factors are proteins that recognize stop codons. The binding of release factors triggers the disassembly of the translational apparatus.

When the ribosome reaches a stop codon within the mRNA strand, a release factor binds to the ribosome. The release factor triggers the disassembly of the translational apparatus and release of the polypeptide chain. The polypeptide chain is released through the hydrolysis of the bond linking the chain to the tRNA. This reaction is catalyzed by peptidyl transferase.

Translation is the process where ribosomes synthesize proteins from an mRNA strand. In eukaryotes, this process occurs in the cytosol with free ribosomes or across the membrane of the endoplasmic reticulum using membrane-bound ribosomes. In prokaryotes, translation occurs in the cytoplasm.

The start codon (AUG) codes for the amino acid methionine. The start codon is the nucleotide triplet on the mRNA strand that signals the start of the codons to be translated. Each codon triplet binds to a complementary anticodon triplet on a tRNA molecule that carries a corresponding amino acid. 

In the initiation stage of translation, a 5’ cap forms at the 5’ end of the mRNA strand, which is composed of the small ribosomal subunit and initiation factors. Initiation factors are proteins that facilitate the start of translation during the initiation stage. Once this complex is assembled, it “scans” the mRNA strand for the start codon, AUG. The initiator tRNA molecule coding the anticodon UAC and carrying the corresponding amino acid methionine is recruited and binds to the start codon. This makes methionine the first amino acid in the polypeptide chain. The large ribosomal subunit then associates with the complex, placing the methionine tRNA in the P-site of the large subunit. There is an alternative model of initiation in which the mRNA scanning complex does not form at the 5’ end. This model is believed to occur under stress responses.