Silent mutations are changes in the nucleotide sequence of DNA that do not result in a change in the amino acid sequence of the protein. These mutations typically occur in the third position of a codon, where due to the redundancy of the genetic code, different codons can code for the same amino acid. For instance, a change from GCU to GCC both code for the amino acid alanine, and thus the mutation does not affect the protein's amino acid sequence. Although silent mutations do not alter the protein's structure or function, they can affect the efficiency and accuracy of protein synthesis, and in some cases, they may have subtle effects on how the protein is processed or regulated.

Stop codons (UAA, UAG, UGA) do not code for any amino acids; instead, they play a critical role in signalling the termination of protein synthesis. These codons are recognised by release factors, proteins that bind to the ribosome when a stop codon is present in the A site. The binding of a release factor to the ribosome triggers a series of reactions leading to the release of the newly formed polypeptide chain from the ribosome. This process ensures that protein synthesis stops at the appropriate point, preventing the production of abnormally long or truncated proteins that could be nonfunctional or harmful to the cell.

The near-universality of the genetic code across different organisms is significant for several reasons. Firstly, it underscores the shared evolutionary origins of all life forms on Earth. This common genetic language suggests that all organisms descended from a common ancestor that used the same code to translate genetic information into proteins. Secondly, the universality of the genetic code has practical implications in biotechnology and genetic engineering. For instance, genes from one organism can often be expressed in another because the same genetic code is used to translate mRNA into proteins. This allows scientists to produce recombinant proteins, such as insulin or growth hormone, in bacteria or other host organisms for medical and industrial applications.

Methionine plays a dual role in protein synthesis. Firstly, it is the amino acid encoded by the start codon AUG, marking the beginning of the protein synthesis process. When a ribosome encounters the AUG codon on mRNA, it signals the start of translation, and methionine is the first amino acid incorporated into the nascent polypeptide chain. Secondly, methionine plays a role in the structure and function of the growing polypeptide. In eukaryotic cells, methionine at the N-terminal (start) of the protein is often removed or modified after translation, which can be crucial for the protein's final function, stability, and location within the cell.

The wobble hypothesis, proposed by Francis Crick, explains the flexibility in the pairing between the codon on mRNA and the anticodon on tRNA, especially at the third base of the codon. According to this hypothesis, the first two bases of the codon pair strictly according to standard base-pairing rules (A-U and G-C), but the third base can wobble, allowing for non-standard base pairing. This means that the anticodon of tRNA can form hydrogen bonds with more than one type of codon. For example, an anticodon with U in the first position can pair with either A or G in the third position of the mRNA codon. This flexibility allows a single tRNA to recognise and pair with multiple codons, reducing the number of tRNA molecules required and increasing the efficiency of protein synthesis.