Patent ID: 8455221

Claim:
A method for determining the copy number of fetal nucleic acid in a sample comprising: (a) contacting under amplification conditions a nucleic acid sample from a pregnant human subject, which sample nucleic acid contains extracellular nucleic acid comprising fetal nucleic acid and maternal nucleic acid, the combination of the fetal species and the maternal species comprising total nucleic acid in the sample, with: (i) a first set of amplification primers that specifically amplify a first region in sample nucleic acid comprising a feature that (1) is present in the fetal nucleic acid and is not present in the maternal nucleic acid, or (2) is not present in the fetal nucleic acid and is present in the maternal nucleic acid, (ii) a second set of amplification primers that amplify a second region in the sample nucleic acid allowing for a determination of the total nucleic acid in the sample, wherein the first region and the second region are different, (iii) one or more first competitor oligonucleotides that compete with the first region for hybridization of primers of the first amplification primer set, and (iv) one or more second competitor oligonucleotides that compete with the second region for hybridization of primers of the second amplification primer set, thereby generating fetal nucleic acid amplification products, total nucleic acid amplification products, first competitor amplification products, and second competitor amplification products, wherein each of the fetal nucleic acid, total nucleic acid, first competitor and second competitor amplification products are of different lengths; (b) separating the fetal nucleic acid amplification products, total nucleic acid amplification products, and competitor amplification products, thereby generating separated fetal nucleic acid amplification products, total nucleic acid amplification products, and competitor amplification products; and (c) determining the copy number of the fetal nucleic acid in the sample based on the separated amplification products.