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 determining genetic data for DNA from cancer cells, comprising:
obtaining cell-free DNA from a blood sample, wherein the cell-free DNA comprises DNA from cancer cells comprising one or more chromosome segments;
ligating at least one adapter to the chromosome segments, wherein the at least one adapter comprises a universal amplification sequence;
performing targeted amplification using a universal primer that binds to the universal amplification sequence, and target-specific primers, to generate amplified nucleic acid molecules; and
determining genetic data for the cell-free DNA from cancer cells by performing next-generation sequencing.
2. The method of claim 1 , wherein the method further comprises detecting a point mutation, insertion or deletion.
3. The method of claim 1 , wherein the next-generation sequencing is performed using sequencing-by-synthesis.
4. The method of claim 1 , wherein the targeted amplification is targeted PCR.
5. The method of claim 1 , wherein the targeted amplification amplifies SNP loci.
6. 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, wherein the sequencing-by-synthesis comprises clonal amplification and measurement of sequences of the clonally amplified DNA; 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.
7. The method of claim 6 , wherein the biological sample is a blood sample.
8. The method of claim 6 , wherein the amplification comprises targeted amplification to amplify the target loci.
9. The method of claim 6 , wherein the amplification further comprises universal amplification.
10. The method of claim 6 , wherein the target loci comprise SNP loci.
11. The method of claim 10 , wherein the confidence that each SNP is correctly called is at least 95%.
12. The method of claim 10 , wherein the confidence that each SNP is correctly called is at least 99%.
13. The method of claim 6 , wherein the genetic data obtained is noisy and comprises allele drop out errors.
14. The method of claim 6 , wherein the genetic data obtained is noisy and comprises measurement bias.
15. The method of claim 6 , wherein the genetic data obtained is noisy and comprises incorrect measurements.
16. The method of claim 6 , further comprising normalizing the genetic data for differences in amplification and/or measurement efficiency between the loci.
17. 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, wherein the target loci comprise SNP loci;
(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.
18. The method of claim 17 , wherein the biological sample is a blood sample.
19. The method of claim 17 , wherein the amplification comprises targeted amplification to amplify the target loci.
20. The method of claim 17 , wherein the amplification further comprises universal amplification.
21. The method of claim 17 , wherein the confidence that each SNP is correctly called is at least 95%.
22. The method of claim 17 , wherein the confidence that each SNP is correctly called is at least 99%.
23. The method of claim 17 , wherein the genetic data obtained is noisy and comprises allele drop out errors.
24. The method of claim 17 , wherein the genetic data obtained is noisy and comprises measurement bias.
25. The method of claim 17 , wherein the genetic data obtained is noisy and comprises incorrect measurements.
26. The method of claim 17 , further comprising normalizing the genetic data for differences in amplification and/or measurement efficiency between the loci.