Fig 1. Study design and blood sample collection.

The schematic illustration of experimental design showing blood sample collection from healthy individuals and cancer patients, and cell-free DNA (cfDNA) quantification steps. A total of 275 fresh blood samples were collected from monozygotic (n = 39) twins, dizygotic (n = 13) twins, sibling pairs (n = 26), genetically unrelated healthy individuals (n = 119), and a total of 90 blood samples from breast (n = 26) and ovarian cancer (n = 64) patients. Plasma was isolated from a fresh blood sample then cfDNA was extracted from plasma and quantified by a fluorometer (ng/ml) and/or by real-time quantitative PCR (copies/ml).