How many nucleotides encode the identity of one of the 20 amino acids and is called a codon

the size of a Codon is 3 nucleotides.

The 20 amino acids are encoded by combinations of four nucleotides

If a codon were two nucleotides, the set of all combinations could only encode 16 amino acids.

since Codons are made up of three nucleotides, the set of all combinations can encode 64 amino acids. {i.e. 64 different combinations of four nucleotides taken three at a time.} But of the total of 64 codons, 61 encode amino acids and 3 specify termination of translation.

I hope this Helps!

desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available. most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly.