There is only one codon that signals the start of translation: AUG. This codon codes for the amino acid methionine so this amino acid will also be at the N-terminus of all proteins, however it may be removed and/or modified later.

Every codon is composed of three RNA nucleobases, and codes for a specific amino acid; however, there can be multiple codons that code for one amino acid. The start codon, AUG, signals the beginning of translation and codes for methionine.

mRNA is the template used during translation. The mRNA strand is read and "translated" into a polypeptide by tRNA.

DNA would be the template for transcription, not for translation.

Missense mutations are point mutations that cause a single amino acid in a protein to be changed. This may or may not affect the functionality of the protein. When one amino acid is replaced by another amino acid from the same class, such as replacing one polar amino acid with another, functionality is usually retained. When an amino acid from a different class is used, such as replacing an acidic amino acid with a basic amino acid, the protein folding may be affected and functionality may fail.

The other answers describe other types of mutations. Silent result in no change to the protein primary structure. Nonsense mutations cause early termination. Frameshift mutations shift the reading frame of the codon sequence, severely altering the protein composition.

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.

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.

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.

The three steps for the elongation process of translation are codon recognition, peptide bond formation, and translocation. These steps essentially correspond to the different tRNA positions in the ribosome. tRNA enters and matches the codon of the mRNA strand. A peptide bond is then formed between the tRNA amino acid and the ribosomal amino acid chain. The empty tRNA and peptide strand then shift to make room for the next residue to enter to ribosome structure.

RNA spicing occurs in the nucleus as part of post-transcriptional modification. Introns are removed to generate a mature mRNA strand before translation can occur.

In translation, the mRNA is positioned in the ribosome and read in the 5'-to-3' direction. Initiation of translation is triggered by a tRNA attached to a methionine entering the P site of the ribosome. The mRNA will then be read, and additional amino acids will be added to the chain, which grows in the P site. New tRNA enters the A site and old tRNA exits the E site, but the amino acid chain is always anchored to the tRNA in the P site.

Elongation continues until a stop codon occupies the A-site of the ribosome. The stop codon is a three-base signal present within the mRNA. There are three stop codons: UAG, UAA, and UGA.

There are three principle steps to translation. Initiation occurs when the ribosomes encounters the start codon, AUG, and recruits a methionine tRNA. Elongation of the polypeptide occurs as the ribosomes continues to recruit tRNA molecules and build the peptide chain. Termination occurs when the ribosome encounters a stop codon and releases the completed polypeptide.