An international team of scientists lead by UC Davis has found genetic markers in European Americans that distinguish ethnic groups, including Greek, German, Italian, Irish, Spanish, Scandinavian, United Kingdom and Ashkenazi Jewish groups. The results, published in Public Library of Science Genetics, will aid efforts to determine risk factors and optimize treatment for complex human diseases, according to Michael Seldin, chair of the Rowe Program in Genetics and a co-author of the study. The team, including first author, graduate student Chao Tian, looked at more than 300,000 single nucleotide polymorphisms, called SNPs, or "snips," in more than 1,000 individuals. SNPs are changes in which a single base in the DNA differs from the usual base at that position. An aberrant SNP can cause disease, like the one responsible for sickle cell anemia.