GENETIC-VARIATION IN PAW PREFERENCE (HANDEDNESS) IN THE MOUSE

Lateralization of paw preference in laboratory mice in a single-paw re aching task has been used as a model system for left- and right-hand u sage. Given a set number of paw reaches for food from a centrally plac ed food tube, an individual mouse will exhibit a reliable number of le ft and right paw reaches. Within any single inbred strain, there are a pproximately equal numbers of left-pawed and right-pawed mice. Neverth eless, significant strain differences have been reported for the degre e of lateralization of paw preference. We report here a systematic sur vey of paw preference in 12 inbred strains of the mouse in which the d egree of lateralization falls into two groups of weakly lateralized an d highly lateralized paw preference. The genetic inference is that a s ingle major gene may control some function, and alternate alleles at t his locus are expressed as weakly and highly lateralized paw preferenc e. Reciprocal crosses indicate the trait is additive with no maternal or X-linked effects. The direction of paw preference has previously ap peared to be genetically neutral, but in some strains there is evidenc e of significant deviation of the numbers of mice to the left and righ t of equal paw usage, independent of degree of lateralization, and thi s suggests that direction of left-right paw usage may be a separate ge netic trait in the mouse model.