History of DNA Testing

DNA testing is a powerful tool for identification. With today’s technology, DNA tests can now identify individuals with almost 100% certainty.

Identification has not always been this conclusive. Before DNA tests, the scientific community used other biological tools to identify people and determine biological relationships. These techniques, which included blood typing, serological testing, and HLA testing, were useful for many different tests (such as matching blood and tissue donors with recipients and reducing the rejection rate for transplant patients), but they were not conclusive for identification and determining biological relationships.

With the introduction of DNA testing in the late 1970s and early 1980s, scientists saw the potential for more powerful tests for identification and determination of biological relationships. Thanks to the advent of DNA testing, we can now definitively determine the identity of individuals and their biological relatives.

The following sections review the development of DNA testing from the early days of blood typing to the latest technology in DNA testing.

Introduction to DNA Testing History

1920’s: Blood Typing 

In the early 1920’s, scientists identified 4 different blood types in humans – A, AB, B, and O – based on the presence of certain proteins called antigens in the blood. The blood typing system, called the ABO system, provided physicians with critical information about their patients, allowing them to safely perform medical procedures like blood transfusions by matching the blood types of donor and recipient.

Scientists realized that blood types were inherited biologically and could predict the blood type of the child based on the biological parent’s blood type. Conversely, if one of the parent’s blood types was unknown, one could use the blood type of the child and the known parent to identify the missing parent’s blood type. However since the information from blood typing is limited, it was difficult to conclusively identify biological relationships. For example, if a child had Type A blood and the child’s mother had Type AB, the child’s biological father could have any one of the 4 blood types. Thus, in this example, no man could be excluded as the child’s biological father. The power of exclusion, the ability to exclude a falsely accused alleged father, for ABO blood testing is about 30%, and not useful for routine paternity testing.


1930’s: Serological Testing

In the 1930’s, scientists discovered other proteins on the surface of blood cells that could be used for identifying people. The Rh, Kell, and Duffy blood group systems, like the ABO blood system, were based on the presence of specific antigens that are biologically inherited and provided additional power, along with ABO, to resolve questioned biological relationships. However, serological testing is not conclusive for resolving question biological relationships. The power of exclusion for serological testing is 40%, meaning this technique alone, like ABO, is not effective in resolving questioned biological relationships.


1970’s: HLA Testing 

In the mid 1970’s, scientists focused on tissue typing and discovered the Human Leukocyte Antigen (HLA), a protein present through out the body except for red cells. White cells found in blood were found to have a high concentration of HLA. It was also discovered that there were many different types of HLA, and the different HLA types varied between people that were not biologically related. Because of the high variability of HLA types among people, HLA was used to answer questions about biological relationships. The power of exclusion of HLA testing is 80% and coupled with ABO and serological testing is about 90%. This test battery ushered in the use of genetic testing to both include and exclude an alleged father. One factor that made HLA testing challenging is that it required a large blood sample that must be tested within a few days of collection. Today, HLA, ABO, and serology are not used routinely for relationship testing and have been replaced with more powerful DNA methods.


1980’s: RFLP DNA Testing

In the early 1980’s, a technique was developed known as Restriction Fragment Length Polymorphism (RFLP) analysis that became the first genetic test using DNA. Like HLA, ABO, and serological tests, DNA is inherited genetically from both biological parents. Scientists discovered regions in the DNA that are highly variable (polymorphic) and more discriminating than HLA and blood proteins. DNA is found in every cell in the body, except red blood cells. These attributes make DNA testing ideal for resolving questioned biological relationships. The RFLP procedure uses enzymes (restriction endonucleases) to cut the DNA and labeled DNA probes to identify the regions that contained VNTRs (Variable Number Tandem Repeats). In a paternity test where the mother, child, and alleged father are tested, half of the child’s DNA should match the biological mother and half should match the biological father. Occasionally, the child’s DNA profile may not match either parent at a single DNA location (locus), possibly caused by a mutation. When this occurs, a calculation is performed to determine whether the observed genetic inconsistency is a mutation or an exclusion. The power of exclusion of RFLP DNA test is greater than 99.99%. However currently this test is not performed routinely because of the amount of DNA required for testing (about 1 microgram) requires a blood sample and the long turn around time required for testing (10 – 14 days).


1990’s: PCR DNA Testing

In the early 1990’s, Polymerase Chain Reaction (PCR) DNA testing replaced RFLP analysis for routine relationship testing. PCR analysis requires less DNA (1 nanogram) so a cheek (buccal) swab is a suitable sample for testing, thus eliminating the necessity of a blood collection. PCR testing is much faster than RFLP generating results within one day of sample delivery to the lab. PCR targets regions in the DNA known as STRs (Short Tandem Repeats) that are highly variable. In a paternity test where the mother, child, and alleged father are tested, the child’s DNA should match both biological parents unless there is a mutation. Statistical calculations can be performed to help determine whether a genetic inconsistency at a single location (locus) is consistent with a mutation or an exclusion. Occasionally more than two genetic inconsistencies are observed and in those cases additional testing is performed. DDC examines a standard battery STR loci, but can test additional STR loci when needed to resolve a case. The power of the PCR DNA test is greater than 99.99%


2000’s: SNP Arrays 

In the early 2000’s, scientists were able to combine thousands of SNP (Single Nucleotide Polymorphism) loci into a single test. SNPs are letter changes in the DNA that can be used as genetic markers for a variety of applications. SNP arrays are not commonly used for relationship testing but are used for a number of other genetic tests including; predisposition to genetic disease, health and wellness, and ancestry. DDC uses a large 800,000 SNP custom array for the GPS Origins™ test. The array contains AIMs (Ancestry Informative Markers), Y-Chromosome markers, mitochondrial markers, ancient DNA markers, and other markers useful for establishing more distant biological relationships like 4th or 5th cousins.


2010’s: Next Generation Sequencing

NGS (Next Generation Sequencing) or Massively Parallel Sequencing is the newest technique available for genetic analysis. This procedure generates a DNA sequence that is the linear arrangement of letters (A, T, C, and G) that occur in a DNA sample. Because the technique allows one to simultaneously start the sequencing at thousands of locations in the DNA that overlap, massive amounts of data can be generated and put back together with appropriate bioinformatics programs. It would be like taking book and cutting out sections of sentences then reassembling the book using a computer program to recognize overlapping sentence fragments.

DDC currently uses NGS for its Non-Invasive Prenatal Paternity Test (NIPP) that can determine the biological father of a fetus as early as 8 weeks gestation using a blood sample from the mother. Before NIPP testing, a chorionic villus sample (cvs) or amniocentesis sample was required from the mother. Both of these procedures are invasive and have a small risk of damage to the fetus. The NIPP test is safe for the fetus and detects circulating cell free fetal DNA (cfDNA) in the mother’s plasma and sequences the DNA to interrogate several thousand SNPs.

DNA testing is a powerful tool for identification. With today’s technology, DNA tests can now identify individuals with almost 100% certainty.

Identification has not always been this conclusive. Before DNA tests, the scientific community used other biological tools to identify people and determine biological relationships. These techniques, which included blood typing, serological testing, and HLA testing, were useful for many different tests (such as matching blood and tissue donors with recipients and reducing the rejection rate for transplant patients), but they were not conclusive for identification and determining biological relationships.

With the introduction of DNA testing in the late 1970s and early 1980s, scientists saw the potential for more powerful tests for identification and determination of biological relationships. Thanks to the advent of DNA testing, we can now definitively determine the identity of individuals and their biological relatives.

The following sections review the development of DNA testing from the early days of blood typing to the latest technology in DNA testing.

Introduction to DNA Testing History

1920’s: Blood Typing 

In the early 1920’s, scientists identified 4 different blood types in humans – A, AB, B, and O – based on the presence of certain proteins called antigens in the blood. The blood typing system, called the ABO system, provided physicians with critical information about their patients, allowing them to safely perform medical procedures like blood transfusions by matching the blood types of donor and recipient.

Scientists realized that blood types were inherited biologically and could predict the blood type of the child based on the biological parent’s blood type. Conversely, if one of the parent’s blood types was unknown, one could use the blood type of the child and the known parent to identify the missing parent’s blood type. However since the information from blood typing is limited, it was difficult to conclusively identify biological relationships. For example, if a child had Type A blood and the child’s mother had Type AB, the child’s biological father could have any one of the 4 blood types. Thus, in this example, no man could be excluded as the child’s biological father. The power of exclusion, the ability to exclude a falsely accused alleged father, for ABO blood testing is about 30%, and not useful for routine paternity testing.


1930’s: Serological Testing

In the 1930’s, scientists discovered other proteins on the surface of blood cells that could be used for identifying people. The Rh, Kell, and Duffy blood group systems, like the ABO blood system, were based on the presence of specific antigens that are biologically inherited and provided additional power, along with ABO, to resolve questioned biological relationships. However, serological testing is not conclusive for resolving question biological relationships. The power of exclusion for serological testing is 40%, meaning this technique alone, like ABO, is not effective in resolving questioned biological relationships.


1970’s: HLA Testing 

In the mid 1970’s, scientists focused on tissue typing and discovered the Human Leukocyte Antigen (HLA), a protein present through out the body except for red cells. White cells found in blood were found to have a high concentration of HLA. It was also discovered that there were many different types of HLA, and the different HLA types varied between people that were not biologically related. Because of the high variability of HLA types among people, HLA was used to answer questions about biological relationships. The power of exclusion of HLA testing is 80% and coupled with ABO and serological testing is about 90%. This test battery ushered in the use of genetic testing to both include and exclude an alleged father. One factor that made HLA testing challenging is that it required a large blood sample that must be tested within a few days of collection. Today, HLA, ABO, and serology are not used routinely for relationship testing and have been replaced with more powerful DNA methods.


1980’s: RFLP DNA Testing

In the early 1980’s, a technique was developed known as Restriction Fragment Length Polymorphism (RFLP) analysis that became the first genetic test using DNA. Like HLA, ABO, and serological tests, DNA is inherited genetically from both biological parents. Scientists discovered regions in the DNA that are highly variable (polymorphic) and more discriminating than HLA and blood proteins. DNA is found in every cell in the body, except red blood cells. These attributes make DNA testing ideal for resolving questioned biological relationships. The RFLP procedure uses enzymes (restriction endonucleases) to cut the DNA and labeled DNA probes to identify the regions that contained VNTRs (Variable Number Tandem Repeats). In a paternity test where the mother, child, and alleged father are tested, half of the child’s DNA should match the biological mother and half should match the biological father. Occasionally, the child’s DNA profile may not match either parent at a single DNA location (locus), possibly caused by a mutation. When this occurs, a calculation is performed to determine whether the observed genetic inconsistency is a mutation or an exclusion. The power of exclusion of RFLP DNA test is greater than 99.99%. However currently this test is not performed routinely because of the amount of DNA required for testing (about 1 microgram) requires a blood sample and the long turn around time required for testing (10 – 14 days).


1990’s: PCR DNA Testing

In the early 1990’s, Polymerase Chain Reaction (PCR) DNA testing replaced RFLP analysis for routine relationship testing. PCR analysis requires less DNA (1 nanogram) so a cheek (buccal) swab is a suitable sample for testing, thus eliminating the necessity of a blood collection. PCR testing is much faster than RFLP generating results within one day of sample delivery to the lab. PCR targets regions in the DNA known as STRs (Short Tandem Repeats) that are highly variable. In a paternity test where the mother, child, and alleged father are tested, the child’s DNA should match both biological parents unless there is a mutation. Statistical calculations can be performed to help determine whether a genetic inconsistency at a single location (locus) is consistent with a mutation or an exclusion. Occasionally more than two genetic inconsistencies are observed and in those cases additional testing is performed. DDC examines a standard battery STR loci, but can test additional STR loci when needed to resolve a case. The power of the PCR DNA test is greater than 99.99%


2000’s: SNP Arrays 

In the early 2000’s, scientists were able to combine thousands of SNP (Single Nucleotide Polymorphism) loci into a single test. SNPs are letter changes in the DNA that can be used as genetic markers for a variety of applications. SNP arrays are not commonly used for relationship testing but are used for a number of other genetic tests including; predisposition to genetic disease, health and wellness, and ancestry. DDC uses a large 800,000 SNP custom array for the GPS Origins™ test. The array contains AIMs (Ancestry Informative Markers), Y-Chromosome markers, mitochondrial markers, ancient DNA markers, and other markers useful for establishing more distant biological relationships like 4th or 5th cousins.


2010’s: Next Generation Sequencing

NGS (Next Generation Sequencing) or Massively Parallel Sequencing is the newest technique available for genetic analysis. This procedure generates a DNA sequence that is the linear arrangement of letters (A, T, C, and G) that occur in a DNA sample. Because the technique allows one to simultaneously start the sequencing at thousands of locations in the DNA that overlap, massive amounts of data can be generated and put back together with appropriate bioinformatics programs. It would be like taking book and cutting out sections of sentences then reassembling the book using a computer program to recognize overlapping sentence fragments.

DDC currently uses NGS for its Non-Invasive Prenatal Paternity Test (NIPP) that can determine the biological father of a fetus as early as 8 weeks gestation using a blood sample from the mother. Before NIPP testing, a chorionic villus sample (cvs) or amniocentesis sample was required from the mother. Both of these procedures are invasive and have a small risk of damage to the fetus. The NIPP test is safe for the fetus and detects circulating cell free fetal DNA (cfDNA) in the mother’s plasma and sequences the DNA to interrogate several thousand SNPs.