Identification of quantitative trait loci for body weight and body weight gain in two growth-differentiated mouse lines. A genome wide quantitative trait locus (QTL) analysis was performed in two lines L and C derived from four mice strains (A.CA, C57BL/6, BALB/c, BN/a). This lines differed in body weight, behaviour, length of reproduction period, rate of ageing, degree survivability. Five statistically significant QTL for body weight at 56 day, body weight gain from 12-21 and from 21-56 were detected. Lines C and L are unique tools for investigating genetic factors that regulate body weight.