Platelet serotonin concentrations in BAC-positive and BAC-negative F2 progeny. Platelet serotonin levels were determined in each of 22 BAC-positive, Slc35d3^{(−/− or +/−)} (•), 9 BAC-negative, Slc35d3^−/− (▪), and 5 BAC-negative Slc35d3^+/− (▴) F2 progeny. Each symbol represents the serotonin concentration in platelets from a single mouse. The average serotonin levels in wild-type C3H/HeSnJ (solid arrow) and ash-Roswell mutants (open arrow) are indicated.