Nucleotide sequence of the 1.2-kb 3'-region and genotype distribution of two common c-myc alleles of the domestic cat.

Nucleotide (nt) sequence analyses of the 1.2-kb BamHI-EcoRI cloned 3'-fragment encompassing the polymorphic SmaI restriction site of the feline c-myc gene reveal that the SmaI site, present in CM2 allele but absent from CM3 allele, is located in intron 2, 134 nt 5' of the exon 3. A G-to-C transversion in CM2 results in the creation of the SmaI site. Additionally, the alleles differ at four other nt positions in intron 2, three of these changes being in a region of the intron which exhibits 80% homology between the feline and human c-myc. The alleles also differ in two nt positions in exon 3 in the third position of the codon resulting, however, in no amino acid alteration. Genotype distribution analysis based on the SmaI polymorphism shows that CM2 homozygosity is rare and its frequency deviates significantly from the expected distribution patterns for independently segregating alleles.