System and method for cleaning noisy genetic data and determining chromosome copy number
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.
1. A method for measuring the amounts of fetal chromosome segments in a maternal blood sample, comprising:
obtaining cell-free DNA comprising fetal and maternal chromosome segments from the maternal blood sample;
performing universal amplification on the chromosome segments to generate amplified chromosome segments;
performing clonal amplification on the amplified chromosome segments to generate clonally amplified chromosome segments; and
measuring the amounts of clonally amplified fetal chromosome segments by performing next-generation sequencing.
2. The method of claim 1 , wherein the fetal chromosome segments map to chromosomes 13, 18, and/or 21.
3. The method of claim 2 , wherein the method is used to detect trisomy at chromosomes 13, 18, and/or 21.
4. The method of claim 1 , wherein at least one adapter is ligated to the chromosome segments before performing universal amplification.
5. The method of claim 4 , wherein the at least one adapter comprises a universal amplification sequence and the universal amplification uses universal primers that bind to the universal amplification sequence.
6. The method of claim 5 , wherein the universal amplification is universal PCR.
7. The method of claim 1 , wherein the next-generation sequencing is performed using sequencing-by-synthesis.
8. The method of claim 1 , wherein the clonally amplified maternal chromosome segments are measured along with the clonally amplified fetal chromosome segments by performing next-generation sequencing.
9. The method of claim 1 , further comprising measuring the amounts of clonally amplified maternal chromosome segments and comparing the measured amounts of clonally amplified maternal chromosome segments with the measured amounts of clonally amplified fetal chromosome segments.
10. The method of claim 1 , wherein the measuring is performed irrespective of allele value.
11. The method of claim 1 , wherein the measuring comprises measurement of alleles having 100% penetrance.
12. The method of claim 1 , wherein the measuring comprises quantitative allele measurements.
13. The method of claim 1 , wherein the method further comprises comparing the measured amounts of fetal chromosome segments for a chromosome segment of interest from the maternal blood sample with measured amounts of fetal chromosome segments for the chromosome segment of interest from reference maternal blood samples that are disomic for the chromosome segment of interest.