Nucleotides are the building blocks of DNA and RNA. They are arranged in sequences of three, called codons, to code for specific amino acids.

Here's a breakdown:

* DNA and RNA: These are the genetic materials that carry the instructions for building and maintaining an organism.

* Nucleotides: These are the individual units that make up DNA and RNA. They consist of a sugar (deoxyribose in DNA, ribose in RNA), a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, thymine in DNA, and uracil in RNA).

* Codons: Each set of three consecutive nucleotides in DNA or RNA forms a codon. Each codon specifies a particular amino acid.

Example: The codon "AUG" in mRNA codes for the amino acid methionine, which is often the start signal for protein synthesis.

Let me know if you have any other questions about nucleotides or genetic code!