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Methods for Non-Invasive Prenatal Ploidy Calling

  • US 20110288780A1
  • Filed: 05/18/2011
  • Published: 11/24/2011
  • Est. Priority Date: 05/18/2010
  • Status: Active Grant
First Claim
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1. A method for determining a ploidy status of a chromosome in a gestating fetus, the method comprising:

  • obtaining a first sample that contains DNA from the mother of the fetus and DNA from the fetus;

    obtaining genotypic data from one or both parents of the fetus;

    processing the first sample by purifying the DNA to obtain a second sample;

    measuring the DNA in the second sample at a set of polymorphic alleles;

    calculating, on a computer, allele ratios at the set of polymorphic alleles from the DNA measurements made on the second sample;

    creating, on a computer, a plurality of ploidy hypotheses concerning expected allele ratios at the set of polymorphic alleles on the chromosome for different possible ploidy states of the chromosome;

    building, on a computer, a joint distribution model for heterozygosity rates of each polymorphic allele on the chromosome for each ploidy hypothesis using genotypic data from the one or both parents of the fetus;

    determining, on a computer, a relative probability of each of the ploidy hypotheses using the joint distribution model and the allele ratios calculated for the second sample; and

    calling the ploidy state of the fetus by selecting the ploidy state corresponding to the hypothesis with the greatest probability.

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