Fluorescence in situ hybridization to chromosomes as a tool to understand human and primate genome evolution

For the last 15 years molecular cytogenetic techniques have been extensively used to study primate evolution. Molecular probes were helpful to distinguish mammalian chromosomes and chromosome segments on the basis of their DNA content rather than solely on morphological features such as banding patterns. Various landmark rearrangements have been identified for most of the nodes in primate phylogeny while chromosome banding still provides helpful reference maps. Fluorescence in situ hybridization (FISH) techniques were used with probes of different complexity including chromosome painting probes, probes derived from chromosome sub-regions and in the size of a single gene. Since more recently, in silico techniques have been applied to trace down evolutionarily derived chromosome rearrangements by searching the human and mouse genome sequence databases. More detailed breakpoint analyses of chromosome rearrangements that occurred during higher primate evolution also gave some insights into the molecular changes in chromosome rearrangements that occurred in evolution. Hardly any "fusion genes" as known from chromosome rearrangements in cancer cells or dramatic "position effects" of genes transferred to new sites in primate genomes have been reported yet. Most breakpoint regions have been identified within gene poor areas rich in repetitive elements and/or low copy repeats (segmental duplications). The progress in various molecular and molecular-cytogenetic approaches including the recently launched chimpanzee genome project suggests that these new tools will have a significant impact on the further understanding of human genome evolution.