Do the MN and Jk systems influence environmental variability in serum lipid levels?

Significant heterogeneity in the distribution of within pair variances of serum total cholesterol, HDL cholesterol, non HDL cholesterol and triglyceride levels has been found in one or both of two samples of MZ twins. We have found some support for the observation of Magnus et al. (1981) that M- pairs have greater environmental variability in cholesterol levels than M+ pairs and weaker evidence that Jka+ pairs are more variable than Jka- pairs. However, these effects appear to be more striking on triglyceride levels. The low power of the variance ratio test is advanced as a possible reason for the inconsistencies in these findings.