When chromosomes are compared in related species which differ widely in DNA content, such differences may be attributed to one of the two causes : (i) lateral multiplication of chromonemata leading to multiple strandedness or (ii) tandem duplication, where length-wise duplication instead of lateral multiplication is responsible for difference in DNA content. This later condition will retain the single stranded feature of chromosomes.
Although multiple strandedness has been demonstrated in several cases of plants like Vicia faba and animals like dipteran salivary gland chromosomes, there are evidences against such a hypothesis to become a generalization. In Vicia faba chromosomes, sub-chromonemata were actually observed, while in related V. sativa they could not be observed. In other genera also like in Allium and Lolium, it has been shown that increase in DNA content is mainly brought about by tandem duplication rather than by lateral multiplication leading to multiple stranded feature. Therefore, the two hypotheses assuming single stranded and multiple stranded nature of chromosomes are complementary and not exclusive to each other.