Comparative Biochemistry

Scientists can study the similarities and differences in the DNA and proteins of different species.Whereas not all comparative biochemistry studies conserved genes and gene products, the most important molecules remain highly conserved among species with only slight changes.Two of the molecules most studied are cytochrome c and ribosomal RNA.Ribosomal RNA has a very slow rate of substitution.Most of the variability will be outside the molecule's functional regions so will be neutral changes.This is called the hypothesis of neutral evolution.Comparing molecular sequences of molecules from two different species can show how closely two different species are related.