Fragile sites in domestic animal chromosomes: molecular insights and challenges

Fragile sites are intriguing cytogenetic phenomena that have been extensively investigated in human and laboratory animal chromosomes over the past 40 years, but domestic animal species have been studied sporadically. Interest in the field has been recently renewed as increasing numbers of fragile site regions are cloned and characterized at the molecular level. Despite much effort, mechanisms by which specific DNA sequence confers fragility to a chromosome region remain unclear. Recent advancements in sequencing and mapping of domestic animal genomes provide tools for molecular characterization of fragile sites in animal chromosomes. Future comparative efforts may contribute insight into both the mechanisms that underlie chromosome fragility, and forces that drive rearrangements observed throughout evolution, and somatic changes that can result in disease or impair fertility.