[ 335 ] Life Science GED ® TEST SCIENCE FLASH REVIEW • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Inside each cell of your body, ribonucleic acid (RNA) contains information to build proteins. A molecule of ribonucleic acid has four nitrogen bases: adenine (A), guanine (G), cytosine (C), and uracil (U). A sequence of three nitrogen bases makes up a codon, which is a unit that codes for one amino acid. How many distinct codons can be made from the nitrogen bases of RNA? Suppose a scientist wanted to make an artificial peptide containing five amino acids (there are 20 possible naturally occurring amino acids that she could use). Without repeating any amino acids, how any permutations are there? The molecular biologist wants to make an artificial RNA codon of three nitrogen bases without repeating any single base and the order does not matter. How many possible combinations are there?