Table 1.

Allelic frequency of mdr1 (del4) mutation in dog breeds worldwide.

Dog Breed	Range of mdr1 (del4) allelic frequency (%)
Collie	48–75
Longhaired Whippet	24–45
Shetland Sheepdog	7–36
(Miniature) Australian Shepherd	16–54
Australian Shepherd	17–46
White Swiss Shepherd	7–16
Old English Sheepdog	0–11
English Shepherd	7
German Shepherd	0–6
Border Collie	0–4

Data retrieved from (Gramer et al., 2011; Geyer and Janko, 2012; Tappin et al., 2012; Monobe et al., 2015; Firdova et al., 2016; Marelli et al., 2020; Soussa et al., 2020). As data availability and sample size differ widely, frequencies have not been listed for all breeds.