which base in codons have a crucial role for determining amino acids the first, second or third

Answer 1

The base in the third position of a codon has a crucial role in determining the amino acid that is encoded. The first and second bases are also important, but they generally denote the same amino acid across different codons due to redundancy in the genetic code. This is known as the "wobble" position, where some variation in the third base can still specify the same amino acid.