Genome variations in the transition from amphibians to reptiles

Summary Many characters differentiate amphibian from reptilian genomes. The former have, on the average, larger and more variable genome sizes, a greater repetitive DNA percentage, and a higher interspersion level among DNAs with different degrees of repetitivity. Reptiles have more reduced and uniform genome sizes, a repetitive DNA percentage generally lower than 50%, and a lower interspersion level. Other differences can be observed in the chromosome banding and in the correlations between genome size and other morphometric and functional parameters of the cell.The differences found in amphibians and reptiles seem to indicate that in these two vertebrate classes there is a different tendency toward or tolerance of the accumulation and preservation of genetically dispensable DNA fractions. This might depend either on a different propensity toward genic amplification or on the appearance, in reptiles, of stricter and more efficient constraints regulating genome size.