Guanine, a nucleotide found in both DNA and RNA

DNA and RNA are polymer chains made of of nucleotides. Nucleotides are logically similar to the amino acids that make up proteins.

Nucleotides are often referred to as bases, short for nucleobase.

Like amino acids, nucleotides have a common backbone portion. The base (nucleobase) is the unique part, and project from the backbone. The base is similar to the sidechain of an amino acid.

The chemistry of DNA, RNA, and proteins is of course different, although carbon, hydrogen, oxygen, and nitrogen are prominently represented in all three. DNA and RNA add phosphorous to the mix, but don't have the sulfur found in some amino acids.

The table below shows the nucleotides for DNA and RNA. Thymine is found only in DNA, while its chemical cousin uracil is found in RNA.

Foldit colors these nucleotides in yellow and purple when "hydro" or a related coloring option is selected. Foldit also classifies them as small or large. When DNA is in its normal double helix configuration, small yellow is bonded with large yellow and small purple is bonded with large purple across the two helixes. These pairings may also occur in RNA, but RNA is more flexible, and many other pairings are possible.

The table also show the codes returned by the function structure.GetAminoAcid. The same codes are used in scientific source such as the PDB.

base code DNA code RNA code color size
Adenine A da ra yellow large
Thymine T dt yellow small
Uracil U ru yellow small
Guanine G dg rg purple large
Cytosine C dc rc purple small
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