In other matches, Maria Sharapova thrashed America's Mallory Burdette 6-1 6-1 to advance to the last 16, while fifth seed Petra Kvitova from Czech Republic beat France's Pauline Parmentier 6-4 6-4.
According to a study carried out by Dr Landau, in co-operation with Marc Parmentier at the Free University of Brussels, and Stephen O'Brien at the National Cancer Institute in Frederick, Maryland, roughly one in every ten Caucasians carries it, although it is strangely absent in African and Asian populations.
Bethanie Mattek-Sands defeated Alize Cornet 7-6 (9-7) 7-5 for her first singles win in the women's teams tournament, while Melanie Oudin beat debutant Pauline Parmentier 6-4 6-4 in the second rubber.