Body Size 1

Body size in dogs is an adaptive trait that can be inherited and has been associated with variants present in several genes, such as IGF1.

Definition

The body size of dogs is influenced by a complex interaction of factors, encompassing both genetic and environmental aspects. These factors include diet, care provided, environmental conditions, age and general health of the dog. Although all of these elements play a significant role, the genetic factor stands out as the primary determinant of dog size. An example of a gene strongly linked to body size in dogs is IGF1.

Genetic basis

The presence of two copies of the variant significantly increases the likelihood that the dog will exhibit a small body size. On the other hand, the absence of either copy increases the chances of the dog developing a large body size. When a single copy of the variant is present, an intermediate phenotype may be manifested. It is important to note that body size in dogs may be influenced by other variants that have not been identified or examined in our test; therefore, the presence or absence of this variant does not guarantee that the dog is necessarily smaller or larger.

Other relevant information

The IGF1 (insulin-like growth factor 1) gene is a strong genetic determinant of body size in mammals, having been related not only to dogs but also to mice and even humans. It has been observed that some large breed dogs presented the variant described here. On this basis, we hypothesize the existence of an as yet unidentified locus associated with body size, which, through an epistatic relationship, may modulate the effect of this variant in some large dog breeds.

Bibliography

Rimbault M, Beale HC, Schoenebeck JJ, et al. Derived variants at six genes explain nearly half of size reduction in dog breeds. Genome Res. 2013 Dec;23(12):1985-95.

Sutter N.B., Bustamante C.D., et al. A Single IGF1 Allele Is a Major Determinant of Small Size in Dogs. Science. 2007 Apr 6; 316(5821): 112–115.