A system generating spontaneous intrachromosomal changes at mitosis inAspergillus nidulans

Abstract

Previous studies had shown that haploid strains ofAspergillus nidulanswhich have a chromosome segment in duplicate are unstable at mitosis. Through the study of various haploid and diploid strains, with and without translocations and with balanced and unbalanced genomes, it has been shown: (1) that imbalance of chromosome segments is responsible for instability, and (2) that the chromosomal deletions produced are confined solely or largely to the segments which provoke instability.The term ‘mitotic non-conformity’ has been proposed for this instability phenomenon. An explanation for it has been sought in terms of attachment sites, limited in number and specific for chromosome segments, at which replication is initiated.