System and method for cleaning noisy genetic data and determining chromosome copy number

Abstract

Disclosed herein is a system and method for increasing the fidelity of measured genetic data, for making allele calls, and for determining the state of aneuploidy, in one or a small set of cells, or from fragmentary DNA, where a limited quantity of genetic data is available. Poorly or incorrectly measured base pairs, missing alleles and missing regions are reconstructed using expected similarities between the target genome and the genome of genetically related individuals. In accordance with one embodiment, incomplete genetic data from an embryonic cell are reconstructed at a plurality of loci using the more complete genetic data from a larger sample of diploid cells from one or both parents, with or without haploid genetic data from one or both parents. In another embodiment, the chromosome copy number can be determined from the measured genetic data, with or without genetic information from one or both parents.

What is claimed is: 
     
         1 . A method for preparing a deoxyribonucleic acid (DNA) fraction from a biological sample useful for analyzing genotypes for DNA from cancer cells, the method comprising:
 (a) extracting cell-free DNA from the biological sample;   (b) producing a fraction of the DNA extracted in (a) by amplifying a plurality of target loci from the DNA to obtain amplification products;   (c) analyzing the fraction of the DNA produced in (b) by
 (i) sequencing the amplification products by sequencing-by-synthesis to obtain genetic data for the plurality of target loci; and 
 (ii) determining the most likely genotypes for DNA from cancer cells based on allele frequencies at the plurality of target loci in the genetic data. 
   
     
     
         2 . The method of  claim 1 , wherein the biological sample is a blood sample. 
     
     
         3 . The method of  claim 1 , wherein the amplification comprises targeted amplification to amplify the target loci. 
     
     
         4 . The method of  claim 1 , wherein the amplification further comprises universal amplification. 
     
     
         5 . The method of  claim 1 , wherein the sequencing-by-synthesis comprises clonal amplification and measurement of sequences of the clonally amplified DNA. 
     
     
         6 . The method of  claim 1 , wherein the target loci comprise SNP loci. 
     
     
         7 . The method of  claim 6 , wherein the confidence that each SNP is correctly called is at least 95%. 
     
     
         8 . The method of  claim 6 , wherein the confidence that each SNP is correctly called is at least 99%. 
     
     
         9 . The method of  claim 1 , wherein the genetic data obtained is noisy and comprises allele drop out errors. 
     
     
         10 . The method of  claim 1 , wherein the genetic data obtained is noisy and comprises measurement bias. 
     
     
         11 . The method of  claim 1 , wherein the genetic data obtained is noisy and comprises incorrect measurements. 
     
     
         12 . The method of  claim 1 , further comprising normalizing the genetic data for differences in amplification and/or measurement efficiency between the loci.