ABSTRACT
In Chapter 2 we studied the structure of DNA and asked how this structure enables genes to play their two roles in living cells, as units of biological information and as units of inheritance. We learned that biological information is encoded in the nucleotide sequence of a DNA molecule, and that complementary base pairing enables DNA molecules to be replicated so that copies can be passed from parents to offspring. Now we must focus more closely on the genes themselves. Knowing that biological information can be encoded in a nucleotide sequence is only the fi rst step in understanding how that information is used by the cell. To take the next step forward we must examine the units of biological information that are contained in individual genes.
