Jan 1, 1993

Heterochromatin study demonstrating the non-linearity of fluorometry useful for calculating genomic base composition

B GodelleS Siljak-Yakovlev


A novel procedure for calculating base-pair frequencies in whole genomes is reported. This has been developed during a study of the role of heterochromatin in microevolution. Closely related species of the Crepis praemorsa complex have similar karyotypes but for their heterochromatin. The changes in relative AT frequency between species have been attributed to heterochromatin sequences by in situ banding of chromosomes with two base-specific fluorochromes. The absolute genome size of species, measured by cytofluorometry, correlated positively with increased karyotypic heterochromatin, as did the proportion of AT bases in the DNA. However, the determination of base content has called for a curvilinear interpretation of data obtained with two base-specific fluorochromes (bisbenzimide Hoechst 33342 and mithramycin), in contrast to the commonly assumed but erroneous direct relationship between fluorescence intensity and base content. Essentially, the fluorochromes' requirements for a sequence of certain base-pairs lead to the notion of Coefficients of Overspecificity: the result is a simple formula for calculating the AT proportion in a genome relative to a reference species from cytometric data, taking account of ligand binding st...Continue Reading

  • References15
  • Citations31

Mentioned in this Paper

Flow Cytometry
Cell Nucleus

Related Feeds


Anthelmintics or antihelminthics are a group of antiparasitic drugs that expel parasitic worms (helminths) and other internal parasites from the body by either stunning or killing them and without causing significant damage to the host. Discover the latest research on anthelmintics here.