The Origin of the Wide Species Variation in Nuclear DNA Content

Abstract

Publisher Summary This chapter discusses the origin of the wide species variation in nuclear DNA content. Evolution depends upon the selection of phenotypes displaying adaptive changes of a heritable nature. The generation of such phenotypes depends on the alteration of genetic information embodied within the DNA of the chromosomes. As for evolutionary change in DNA amount , there is a progression from low DNA content in primitive phyla, such as bacteria to high DNA content in cells of sophisticated higher plants and animals. The causes of change in DNA amount are illustrated in the chapter. Polyploidy, common in plant groups such as the angiosperms and pteridophytes, is a special case as it involves amplification of all genes and all base sequences of the haploid complement. There is an extensive and widespread variation in DNA amount, which is independent of alteration in chromosome number. This is attributable to the amplification or reduction of DNA segments within chromosomes.