MIXED SEGREGATION AND RECOMBINATION OF CHROMOSOMES AND YACS DURING SINGLE-DIVISION MEIOSIS IN SPO13 STRAINS OF SACCHAROMYCES-CEREVISIAE

Diploid yeast strains, homozygous for the mutation spo13, undergo a si ngle-division meiosis and form dyads (two spores held together in one ascus). Dyad analysis of spo13/spo13 strains with centromere-linked ma rkers on five different chromosomes and on a pair of human DNA YACs sh ows that: (a) in spo13 meiosis, chromosomes undergo mixed segregation, namely some chromosomes segregate reductionally whereas others, in th e same cell, segregate equationally; (b) different chromosomes exhibit different segregation tendencies; (c) recombination between homologou s chromosomes might not determine that a bivalent undergoes reductiona l rather than equational segregation.