Re-sequencing of DNA from a diverse panel of cattle reveals a high level of polymorphism in both intron and exon

Ln order to assess the extent of DNA sequence variation in cattle, introns and exons from both the leptin and Amyloid Precursor Protein (APP) genes ha ve been sequenced in a panel of DNAs derived from 22 diverse animals. Direc t DNA sequencing of PCR products was used; thus, 44 chromosomes were studie d. Polymorphisms were identified by manual scanning of sequence chromatogra ms and computerized sequence analysis. Twenty Single Nucleotide Polymorphis ms (SNPs) were detected in 1788 bp sequenced from the leptin gene, giving a frequency of 1 SNP per 89 bp. Twenty-four SNPs were detected in a 458-bp f ragment of the APP gene; 23 of the polymorphisms were contained in a 302-bp intron 16 fragment. This equates to an SNP frequency of 1 per 13 bp for th e intron. We can thus conclude that this portion of the bovine APP gene con stitutes a hypermutable region. Nucleotide sequence diversity values of 0.0 19 and 0.0026 were obtained for APP and leptin respectively.