title: The genetic instability and mutagenic interaction of chromosomal duplications present together in haploid strains of Aspergillus nidulans.
abstract: Previous work has shown that strains of Aspergillus nidulans with a chromosome segment in duplicate (one in normal position, one translocated to another chromosome) are unstable. Deletions occur from either duplicate segment. The present work has shown that when a chromosome I duplication and a chromosome III duplication are together in a haploid, deletions from the intact III duplication generally precede deletions from particular sections of the I duplication. Furthermore, the III duplication can enhance to some (but not major) extent the frequency of deletions from the I duplication. After the III duplication becomes reduced in size as a result of the loss of chromosomal material from the translocated duplicate III segment, such a reduced III duplication can greatly enhance the frequency of deletions from the I duplication. In other words, a III duplication of reduced size can promote far more deletions from the I duplication than the intact III duplication. The major increase in the deletional instability of the I duplication as promoted by the reduced III duplication is confined to the translocated duplicate I segment. The reduced III duplication can induce deletions from a section of the translocated duplicate I segment in accord with a temporal programme, and it appears that a particular region of the I duplication is far more under the mutagenic influence of the reduced III duplication than another region. Moreover, there is indication that there is a differential effect of two generally different genetic backgrounds on the susceptibility of duplication-regions to deletion. Possible mechanisms involved in such chromosomal instability are proposed. A manner in which genetic instability may be related to development is also proposed.
mesh_terms: D001233:Aspergillus nidulans / Q000254:growth & development; D001710:Biotin / Q000378:metabolism; D002869:Chromosome Aberrations; D002872:Chromosome Deletion; D003434:Crossing Over, Genetic; D006238:Haploidy; D009154:Mutation; D010641:Phenotype; D010858:Pigmentation; D013696:Temperature; D014178:Translocation, Genetic
chemical_list: D001710:Biotin