Final answer:
There are 20 unique amino acids encoded by 61 codons in the genetic code, ignoring the three stop codons. The code is unambiguous and redundant, meaning each amino acid can be encoded by multiple codons, which reduces the impact of mutations.
Step-by-step explanation:
Ignoring the stop codons, there are 20 unique amino acids encoded by the genetic code. With four different nucleotides, there are 64 possible combinations to form three-letter codons, but only 61 of these specify amino acids as three are stop codons. The genetic code is both unambiguous and redundant, meaning that while each codon specifies only one amino acid, multiple codons can encode the same amino acid. For example, the amino acid threonine is encoded by four different codons.
This redundancy is beneficial because it provides a buffer against mutations. If the third nucleotide in a codon changes, often called the 'wobble position', it might still result in the same amino acid being incorporated into the protein, reducing the impact of genetic mutations.
One way to understand this is by looking at the codons for glycine, which are similar to each other, primarily differing at the third nucleotide position. This exemplifies how the redundancy of the genetic code can lead to a robustness in the face of potential errors during DNA replication or transcription.