Genetic Control of Blood Pressure by More than One Pair of Alleles 1

Summary and Conclusion

This experiment was designed to determine whether the genetic differences in blood pressure found between the A/J and BALB/cJ and between the A/J and SWR/J strains were due to different loci in the BALB/cJ and SWR/J strains or due to different alleles carried at the same locus. It was found that after four generations of selection the mean blood pressure of the SWR/J was exceeded by 7 mm Hg in males and 17 mm Hg in the females. The results could not be due to different alleles at the same locus since the selected genotype would be the same as the SWR/J genotype at that locus and should not have a more elevated blood pressure than the SRW/J strain. Since the blood pressure in the selected line exceeded that of the SRW/J, each of the two strains (BALB/J and SWR/J) must have contributed different alleles at more than one locus to the original gene pool in the F₁ and F₂. It is also concluded on the basis of genetic selection theory, that the difference between mean systolic blood pressure of the two inbred strains is due to the action of at least three loci.