Question

skill level: to be determined a(n) is a three-letter code word in the genetic code.

Explanation:

In the context of genetics (a subfield of Biology, which is part of Natural Science), a codon is a three - letter sequence of nucleotides (A, U, C, G in RNA or A, T, C, G in DNA) that codes for a specific amino acid or serves as a start/stop signal in the genetic code. So the term that fits here is "codon".

Answer:

codon