Assay systems for genetic analysis

A method for detection of the presence or absence of a fetal copy number variation (CNV) of a genomic region and determination of genetic status of one or more maternal and/or fetal loci of interest in a maternal plasma or serum sample comprising fetal and maternal cell-free DNA, the method comprising:

• (a) hybridizing (i) a first set of at least 24 pairs of fixed sequence oligonucleotides with (ii) fetal and maternal cell-free DNA in the maternal plasma or serum sample, wherein the oligonucleotides of each pair are complementary to regions in first non-polymorphic loci within a first nucleic acid region of interest of a first chromosome or a portion of the first chromosome, and wherein the melting temperatures (Tms) of first fixed sequence oligonucleotides of each of the pairs of the first set vary in a range of two degrees centigrade;
• (b) hybridizing (i) a second set of at least 24 pairs of fixed sequence oligonucleotides with (ii) the fetal and maternal cell-free DNA in the maternal plasma or serum sample, wherein the oligonucleotides of each pair are complementary to regions in second non-polymorphic loci within a second nucleic acid region of interest of a second chromosome or a portion of the second chromosome and wherein the Tms of first fixed sequence oligonucleotides of each of the pairs of the second set vary in a range of two degrees centigrade;
• (c) annealing bridging oligonucleotides to the first and second non-polymorphic loci, wherein the bridging oligonucleotides hybridize between and adjacent to the hybridized oligonucleotides of the first and second sets of fixed sequence oligonucleotide pairs to create adjacently hybridized oligonucleotides spanning the non-polymorphic loci in the first and second nucleic acid regions of interest;
• (d) ligating the adjacently hybridized bridging oligonucleotides and fixed sequence oligonucleotides to produce contiguous ligation products;
• (e) amplifying the contiguous ligation products to produce amplification products, and further amplifying one or more selected nucleic acid regions comprising the one or more loci of interest in the maternal and fetal cell-free DNA in the maternal plasma or serum sample with primers complementary to the selected nucleic acid regions comprising the one or more loci of interest to produce amplified selected maternal and fetal nucleic acid regions in the maternal plasma or serum sample;
• (f) detecting the amplification products to count the relative frequency of each non-polymorphic locus within the first and second nucleic acid regions of interest;
• and
• (g) detecting a fetal CNV of the first nucleic acid region of interest in the maternal serum or plasma sample relative to the second nucleic acid region of interest, and determining if the amplified selected maternal and fetal nucleic acid regions from the one or more loci of interest are detected in a frequency indicative of maternal and/or fetal status of the one or more loci of interest.

A method for detection of the presence or absence of a fetal chromosomal aneuploidy of a first chromosome and determination of genetic status of one or more maternal and/or fetal loci of interest in a maternal plasma or serum sample comprising fetal and maternal cell-free DNA, the method comprising:

• (a) hybridizing (i) a first set of at least 24 pairs of fixed sequence oligonucleotides with (ii) the fetal and maternal cell-free DNA in the maternal plasma or serum sample, wherein the oligonucleotides of each pair are complementary to regions in first non-polymorphic loci within a first chromosome or a portion of the first chromosome, and wherein the melting temperatures (Tms) of first fixed sequence oligonucleotides of each of the pairs of the first set vary in a range of two degrees centigrade;
• (b) hybridizing (i) a second set of at least 24 pairs of fixed sequence oligonucleotides with (ii) the fetal and maternal cell-free DNA in the maternal plasma or serum sample, wherein the oligonucleotides of each pair are complementary to regions in second non-polymorphic loci within a second chromosome or a portion of the second chromosome and wherein the Tms of first fixed sequence oligonucleotides of each of the pairs of the second set vary in a range of two degrees centigrade;
• (c) annealing bridging oligonucleotides to the first and second non-polymorphic loci, wherein the bridging oligonucleotides hybridize between and adjacent to the hybridized oligonucleotides of the first and second sets of fixed sequence oligonucleotide pairs to create adjacently hybridized oligonucleotides spanning the non-polymorphic loci in the first and second chromosomes of interest;
• (d) ligating the adjacently hybridized bridging oligonucleotides and fixed sequence oligonucleotides to produce contiguous ligation products;
• (e) amplifying the contiguous ligation products to produce amplification products, and further amplifying one or more selected nucleic acid regions comprising the one or more loci of interest in the maternal and fetal cell-free DNA in the maternal plasma or serum sample with primers complementary to the selected nucleic acid regions comprising the one or more loci of interest to produce amplified selected maternal and fetal nucleic acid regions in the maternal plasma or serum sample;
• (f) detecting the amplification products to count the relative frequency of each non-polymorphic locus within the first and second chromosomes of interest;
• and
• (g) detecting a fetal chromosomal aneuploidy of the first chromosome in the maternal serum or plasma sample if the relative frequencies of the first and second chromosome of interest vary statistically, and determining if the amplified selected maternal and fetal nucleic acid regions from the one or more loci of interest are detected in a frequency indicative of maternal and/or fetal status of the one or more loci of interest.

A method for detection of the presence or absence of a fetal chromosomal aneuploidy of a first chromosome and determination of genetic status of one or more maternal and/or fetal loci of interest in a maternal plasma or serum sample comprising fetal and maternal cell-free DNA, the method comprising:

• (a) hybridizing (i) a first set of at least 24 pairs of fixed sequence oligonucleotides with (ii) the fetal and maternal cell-free DNA in the maternal plasma or serum sample, wherein the oligonucleotides of each pair are complementary to regions in first non-polymorphic loci within a first chromosome or a portion of the first chromosome, wherein the melting temperatures (Tms) of first fixed sequence oligonucleotides of each of the pairs of the first set vary in a range of two degrees centigrade, and wherein at least one of the fixed sequence oligonucleotides in each pair of the first set of fixed sequence oligonucleotides comprises a locus index;
• (b) hybridizing (i) a second set of at least 24 pairs of fixed sequence oligonucleotides with (ii) the fetal and maternal cell-free DNA in the maternal plasma or serum sample, wherein the oligonucleotides of each pair are complementary to regions in second non-polymorphic loci within a second chromosome or a portion of the second chromosome, wherein the Tms of first fixed sequence oligonucleotides of each of the pairs of the second set vary in a range of two degrees centigrade, and wherein at least one of the fixed sequence oligonucleotides in each pair of the second set of fixed sequence oligonucleotides comprises a locus index;
• (c) annealing bridging oligonucleotides to the first and second non-polymorphic loci, wherein the bridging oligonucleotides hybridize between and adjacent to the hybridized oligonucleotides of the first and second sets of fixed sequence oligonucleotide pairs to create adjacently hybridized oligonucleotides spanning the non-polymorphic loci in the first and second chromosomes of interest;
• (d) ligating the adjacently hybridized bridging oligonucleotides and fixed sequence oligonucleotides to produce contiguous ligation products;
• (e) amplifying the contiguous ligation products to produce amplification products, and further amplifying one or more selected nucleic acid regions comprising the one or more loci of interest in the maternal and fetal cell-free DNA in the maternal plasma or serum sample with primers complementary to the selected nucleic acid regions comprising the one or more loci of interest to produce amplified selected maternal and fetal nucleic acid regions in the maternal plasma or serum sample;
• (f) detecting the amplification products to count the relative frequency of each non-polymorphic locus within the first and second chromosomes of interest;
• and
• (g) detecting a fetal chromosomal aneuploidy of the first chromosome in the maternal serum or plasma sample if the relative frequencies of the first and second chromosome of interest vary statistically, and determining if the amplified selected maternal and fetal nucleic acid regions from the one or more loci of interest are detected in a frequency indicative of maternal and/or fetal status of the one or more loci of interest.