Allelic frequencies of nt230(del4) MDR1 mutation in six related breeds (from top to bottom: Border Collie, Australian Shepherd, Collie, German Shepherd Dog, Shetland Sheepdog and White Swiss Shepherd) in Israel, USA, Europe, UK, Japan and Australia (footnotes 1 to 6 respectively with the relevant literature in the bottom of the panel). Dogs number is given on top of each panel as n. Bar graph indicate allele frequency of each breed, pie graph indicate allelic frequencies of nt230(del4) MDR1 mutation as follows: pale gray for normal (+/+), gray for heterozygote (+/−) and black for homozygote (−/−)