System and method for cleaning noisy genetic data from target individuals using genetic data from genetically related individuals
A system and method for determining the genetic data for one or a small set of cells, or from fragmentary DNA, where a limited quantity of genetic data is available, are disclosed. Genetic data for the target individual is acquired and amplified using known methods, and poorly measured base pairs, missing alleles and missing regions are reconstructed using expected similarities between the target genome and the genome of genetically related subjects. In accordance with one embodiment of the invention, incomplete genetic data is acquired from embryonic cells, fetal cells, or cell-free fetal DNA isolated from the mother's blood, and the incomplete genetic data is reconstructed using the more complete genetic data from a larger sample diploid cells from one or both parents, with or without genetic data from haploid cells from one or both parents, and/or genetic data taken from other related individuals.
1. A method for preparing a preparation of amplified DNA from a sample comprising cell-free DNA derived from a fetus and mother of the fetus useful for detecting the presence or absence of a chromosomal abnormality in the fetus, the method comprising:
(a) extracting cell-free DNA from a blood, serum or plasma sample of the mother of the fetus;
(b) preparing a preparation of amplified DNA by performing targeted multiplex amplification on the cell-free DNA obtained in (a) or DNA derived therefrom to amplify at least 70 target loci on a chromosome or chromosome segment of interest in a single reaction to obtain amplicons;
(c) analyzing the preparation of amplified DNA obtained in (b) by microarray or sequencing to detect amplified DNA to measure the amounts of genetic material at the target loci, wherein the target loci have alleles with 100% penetrance in the population; and determining the presence or absence of a chromosomal abnormality in the fetus based on the measured amounts of genetic material at the target loci.
2. The method of claim 1 , wherein microarray is used to measure the amounts of genetic material at the target loci.
3. The method of claim 1 , wherein sequencing is used to measure the amounts of genetic material at the target loci.
4. The method of claim 1 , wherein the chromosome or chromosome segment of interest is selected from the group consisting of chromosome 13, chromosome 18, chromosome 21, X chromosome, Y chromosome, and combinations thereof, and wherein the chromosomal abnormality is selected from the group consisting of monosomy, uniparental disomy, trisomy, other aneuploidies, unbalanced translocations, insertions, deletions, and combinations thereof.
5. The method of claim 1 , wherein the chromosomal abnormality is trisomy of chromosome 13, chromosome 18, or chromosome 21.
6. The method of claim 1 , wherein the determining is performed by comparing the amounts of genetic material at the target loci to an expected amount, wherein the expected amount is a mean value of genetic material at multiple loci for a reference chromosome or chromosome segment expected to be disomic.
7. The method of claim 1 , wherein the method further comprises determining the probability of aneuploidy in the fetus by comparing the measured amounts of genetic material at the target loci to an expected amount for a particular copy number of a chromosome or chromosome segment of interest.
8. The method of claim 1 , wherein the amplification comprises ligating oligonucleotides that hybridize to target sequences comprising the target loci and amplifying the ligated oligonucleotides by PCR.
9. The method of claim 8 , wherein the PCR is performed using universal primer sequences.
10. A method for preparing a preparation of amplified DNA from a sample comprising cell-free DNA derived from a fetus and mother of the fetus useful for detecting the presence or absence of a chromosomal abnormality in the fetus, the method comprising:
(a) extracting cell-free DNA from a blood, serum or plasma sample of the mother of the fetus;
(b) preparing a preparation of amplified DNA by performing targeted multiplex amplification on the cell-free DNA obtained in (a) or DNA derived therefrom to amplify at least 70 target loci on a chromosome or chromosome segment of interest in a single reaction to obtain amplicons;
(c) analyzing the preparation of amplified DNA obtained in (b) by microarray or sequencing to detect amplified DNA to measure the amounts of genetic material at the target loci, wherein the amounts of genetic material at the target loci are measured irrespective of the identity of alleles at each locus; and determining the presence or absence of a chromosomal abnormality in the fetus based on the measured amounts of genetic material at the target loci.
11. The method of claim 10 , wherein microarray is used to measure the amounts of genetic material at the target loci.
12. The method of claim 10 , wherein sequencing is used to measure the amounts of genetic material at the target loci.
13. The method of claim 10 , wherein the chromosome or chromosome segment of interest is selected from the group consisting of chromosome 13, chromosome 18, chromosome 21, X chromosome, Y chromosome, and combinations thereof, and wherein the chromosomal abnormality is selected from the group consisting of monosomy, uniparental disomy, trisomy, other aneuploidies, unbalanced translocations, insertions, deletions, and combinations thereof.
14. The method of claim 10 , wherein the chromosomal abnormality is trisomy of chromosome 13, chromosome 18, or chromosome 21.
15. The method of claim 10 , wherein the determining is performed by comparing the amounts of genetic material at the target loci to an expected amount, wherein the expected amount is a mean value of genetic material at multiple loci for a reference chromosome or chromosome segment expected to be disomic.
16. The method of claim 10 , wherein the method further comprises determining the probability of aneuploidy in the fetus by comparing the measured amounts of genetic material to an expected amount for a particular copy number of a chromosome or chromosome segment of interest.
17. The method of claim 10 , wherein the amplification comprises ligating oligonucleotides that hybridize to target sequences comprising the target loci and amplifying the ligated oligonucleotides by PCR.
18. The method of claim 17 , wherein the PCR is performed using universal primer sequences.