10. how is it that a code consisting of only four letters (a, t, g, c) can contain instructions for all the different parts of an organism and account for the diversity of organisms on this planet?

The response for this question: How is it that a code consisting of only four letters (A, T, G, C) can contain instructions for all the different parts of an organism and accout for the diversity of organisms on this planet, would be: These letters, known as nucleotide bases, when paired together, can each code for a wide variety of amino acids, the building blocks of proteins. It is proteins that carry out the instructions that are written in the genetic code and each amino acid in a protein can be coded for by more than one of the organized nucleotide pairings.

Therefore, during the process of translation, meaning DNA-RNA-protein, although the nucleotide pairings are pretty basic and limited, each of them, when interpreted by ribosomes and their accompanying tRNA, will call in different types of amino acids and build different types of proteins, depending on the need, the purpose and the location where these proteins will have to act.

This is how from a limited group of DNA nucleotide pairings, it is possible to have so many differences not only within the same organism, but among all living organisms that exist.