A) There are three nucleotide in each codon, and each of these nucleotides can have one of four different bases. How many possible unique codons are there? b) If DNA had only two types of bases instead of four, how long would codons need to be to specify all 20 amino acids?

Explanation:

There are 64 possible codons to be specified for, If we have three nucleotides with 4 bases the set of all combinations can encode

4x4x4 = 64 amino acids

This will give 64 different combinations of four nucleotides

If we have 2 bases with 4 nucleotide we have a possibility of having 16 codons specifying for 20 amino acid.

If we have 2 nucleotides with 4 bases the set of combination is

4×4 = 16 amino acids of four nucleotides

well the answer is 2!