Two duplications have occurred relative to the Doc{}CHKov1Doc1420 progenitor chromosome, both of which involve partial sequences of both CHKov1 and CHKov2. The first duplication includes a large portion of the 5' end of CHKov1 (including some upstream intergenic sequence) and approximately two-thirds of the 3' end of CHKov2. The second duplication is in reverse orientation and includes all of CHKov2 and the 5' end of CHKov1. In both cases the duplicated portions of CHKov1 include part of the Doc element that is inserted in the CHKov1 open reading frame in the progenitor chromosome, with less of the element being duplicated in the reverse oriented second duplication. Exactly the same portion of the CHKov1 coding region and an identical region of upstream intergenic sequence is present in both duplications.
Homozygotes carrying Dp(3;3)CHKov are highly resistant to Sigma virus.
The rearranged Dp(3;3)CHKov chromosome shows increased resistance compared to the progenitor chromosome which carries a Doc insertion in CHKov1 (Doc{}CHKov1Doc1420). Since the rearrangement amplifies the region coding for CHKov1 containing the Doc insertion, the simplest explanation for the increased resistance of the Dp(3;3)CHKov chromosome is that the amplification of the region coding for CHKov1 containing Doc increases the resistance (since in the progenitor chromosome, the Doc{}CHKov1Doc1420 insertion results in increased resistance to Sigma virus compared to the susceptible ancestor). However, the expression of CHKov1
Mutant that interferes with the normal multiplication of some strains of sigma virus, as indicated by delayed acquisition of CO[[2]] sensitivity following viral injection.
Isolated from a Paris stock.
The resistant allele of the 'ref(3)D' gene isolated from a Paris line corresponds to the Dp(3;3)CHKov rearrangement.
