Fig. 2.

Mechanisms that can result in LOH. (A) LOH due to mitotic recombination: short-range LOH can arise from gene conversion between homologous chromosomes (Hom a and Hom b) or from double crossovers (XO); long-range LOH events can arise from single crossovers followed by mitotic segregation or from break-induced replication (BIR). (B) Events due to chromosome missegregation: chromosome nondisjunction yields aneuploid cells monosomic for that chromosome (b) as well as cells carrying an extra copy of the homolog (aab). Events due to reduplication of the monosomic chromosome via a subsequent nondisjunction event or by unlicensed rereplication can generate a strain that is homozygous but disomic for that chromosome (bb).