Classification of genes, rearrangements and chromosomes according to the chromosome field

The study of over 700 species, from algae to humans, reveals that specific DNA sequences, have an optimal territory within the centromere-telomere field. These DNA sequences have maintained their territory within the chromosome field for millions of years irrespective of variation in arm length, of change in chromosome type and of species evolution. Some of these DNA sequences have been isolated biochemically or analysed at the molecular level. They include, e.g., the proximal heterochromatic segments, the genes for ribosomal RNA, and the telomeric heterochromatin. Order prevails in the eukaryotic chromosome. This order allows classification of genes, rearrangements and chromosomes on a genetic basis. Genes are classified as centrons, medons and telons. Rearrangements are classified as: conservative, discordant, disruptive, destructive and incompatible. Chromosomes are also classified depending on their length, arm size and number. These chromosome properties and features now acquire an organizatory meaning which they lacked previously. The available molecular information supports the evidence from the field. The study of the split gene reveals that it is the relative position of the DNA sequences which determines their function. On the basis of the chromosome field, predictions can be made concerning gene organization, gene function and chromosome evolution.