Recognition of DNA Base Sequence Differences among Vertebrates

Abstract

UNLIKE the wide variation of DNA base composition found in bacteria, higher organisms tend to have a restricted average base composition, (vertebrates ∼ 42 moles per cent guanine + cytosine)¹. Thus physical methods such as thermal denaturation or equilibrium density gradient sedimentation, which are useful in distinguishing bacterial DNAs², do not discriminate to any extent among vertebrate DNAs, excluding the question of satellite bands. Phylogenetic relationships among bacteria, based on other criteria, are largely borne out by DNA–DNA hybridization³. While the latter technique can discriminate among distantly related higher organisms⁴ it can be applied with only limited confidence to more closely related vertebrates.