TABLE 1.

Loss of chromosome VII in haploid strains^a

Genotype	Frequency (%) of chromosome loss (mean ± SD)
	Spontaneousb	X-ray inducedc
rad52 CDC5 CKB2d	1.2 ± 0.21	16.3 ± 4.2
rad52 cdc5-ad CKB2d	0.26 ± 0.07	1.7 ± 1.2
rad52 CDC5 ckb2	0.29 ± 0.02	1.9 ± 1.4
rad51 CDC5	0.30 ± 0.071	13.8 ± 0.41
rad51 cdc5-ad	0.073 ± 0.21	5.5 ± 1.1

^aStrains used harbored an extra copy of chromosome VII, which contains the CYH2 and ADE3 genes. 

^bStrains were plated onto medium containing cycloheximide, which selects for cells that have lost the CYH2 gene on the extra chromosome (see also Fig. 3). 

^cCells were plated on nonselective medium and immediately X-irradiated with 2 (rad52 strains) or 3 (rad51 strains) kilorads. 

^dThis strain is pictured in Fig. 2.