Independent segregation of canine I-GS and CUBNloci. (A) Four introns (horizontal lines) and included exons (vertical boxes) were defined by PCR amplification using CUBNcDNA primers and sequencing the products. A 17-bp variation (vertical line) was found in the 0.9-kb intron for which dog F274, an obligate carrier of canine I-GS, was heterozygous and dog F284, an affected dog, was homozygous. (B) Solid symbols indicate I-GS affected dogs, half-solid symbols indicate obligate carriers, squares are males, and circles are females. DNA from offspring of matings between dogs F274 and F284 was amplified by PCR using primers flanking the 17-bp variation, producing allele-specific products of 199 and 182 bp. Results of 10 offspring are shown, with the stars indicating recombinants.