Parkinson disease (PD) is a neurodegenerative disease that has been associated with a significant number of different genes, therefore showing it to be genetically heterogenic. One recent study in 278 families found evidence of two such possible loci. Evidence for linkage to chromosome 18q11 was presented by Gao et al. in 2009. Which of the following would be considered reputable evidence for this?

A. finding the Lod score for association between the chromosomal location and PD to be 4.1
B. finding the locus to be in Hardy-Weinberg equilibrium in the population
C. lack of quantitative difference for the occurrence of both in individuals
D. analysis of all other possible SNPs with no such association to chromosome 18
E. use of persons from multiple ethnic and geographic backgrounds in the study