What are synonyms in the context of codons?

Synonyms in the context of codons refer to sets of codons that specify the same amino acid. This phenomenon arises from the redundancy in the genetic code, where multiple codon sequences can correspond to a single amino acid. For instance, both UUA and UUG code for the amino acid leucine. This redundant nature of the code allows for a degree of flexibility in protein synthesis, as certain codons can be utilized interchangeably without altering the resulting protein's structure.

The other options, while related to codons, highlight different aspects: some refer to codons that code for different amino acids, which would not be synonyms, while others mention codons that are unused in translation or are absent from RNA altogether, neither of which fits the definition of synonyms within this context. Understanding codon synonymy aids in grasping the broader implications of genetic coding and the molecular mechanisms of protein synthesis.