DNA Fingerprinting in Health and Diagnosis

In the history of scientific exploration, few techniques have displayed the transformative power of DNA fingerprinting. Known for its cutting-edge role in solving criminal mysteries, this technology holds a far-reaching impact that extends well beyond forensic investigations. Beyond courtroom drama and investigation, DNA fingerprinting emerges as a key in the realm of healthcare, paving the way for disease diagnosis, personalized therapies, and a profound understanding of our genetic makeup.

DNA fingerprinting is most often used to examine and evaluate the genetic material in our cells to identify a criminal. However, the DNA fingerprinting technology used by forensic scientists can also help with disease diagnosis, management, and therapy, as it helps to “identify organisms causing a disease” and identify genetic disorders that one might carry but not necessarily express. DNA fingerprinting of family members can also help understand whether future children and/or other family members might carry a disease, by analyzing the DNA pattern and chromosomal makeup of a person’s genetics.

In the growing field of personalized therapy, where an individual’s genetic profile tailors the therapeutic and medical intervention for their disease, DNA fingerprinting can provide crucial data. For instance, it can help in identifying genetic matches for organ or marrow donation.

DNA fingerprinting has already been lending a hand to cancer treatment, specifically through the fingerprinting of chemical modifications. Tumors, which are composed of clumps of cancerous cells, have different DNA profile due to the genetic changes of the cancerous cells. With the help of molecular biologists, bioanalysts, and pathologists, researchers have been able to precisely measure and identify “850,000 possible [DNA] sites in genes with or without a methyl group” (Science News). The presence or absence of a methyl group can affect whether a specific part of DNA is expressed at all, and such differences can be responsible for making a healthy cell turn cancerous. Due to this analysis, over 82 tumor types can be classified “very accurately based on the chemical changes of their DNA” (Science News). With the tumor type more easily and precisely identified in an individual, patients can receive appropriate, personalized therapy, improving survival chances and reducing side effects. A similar fingerprinting approach to identifying cell biomarkers, which can be molecules or characteristics (such as blood pressure) indicating the presence of a genetic change, condition, or disease, has led scientists such as Dr. Cynthia Murray at the Lawrence Berkeley National Laboratory to detect and diagnose Alzheimer’s earlier.

Besides detecting mutations and genetic changes, studying the DNA bases as forensic scientists and health professionals do can provide insight into what caused those changes in the sequence of DNA (these changes are also called mutations). A study by the Wellcome Sanger Institute at the University of California, San Diego worked to develop a collection of DNA mutational “signatures” that hadn’t been recorded before, as they “identified almost every publicly available cancer genome at the start of this project and analyzed their whole genome sequences.” This, they say, could now help researchers across the globe understand how these mutations might respond to drugs, as well as some of the chemicals that might be responsible for those mutations. Professor Yuri Dubrova from the NI Vavilov Institute of General Genetics, Moscow has worked with groups of people exposed to radiation – whether they were victims of the Nagasaki and Hiroshima bombings or intentionally exposed to radiation for treatment – to study their mutations and mutational signatures. His continued analysis in this ongoing study can help provide more clarity on how radiation affects genetic changes and whether mutations eventually become “heritable mutations.”

As of now, commercial DNA testing as operated by Ancestry.com, 23andMe, and other ancestry services also provides information directly to the consumer on health conditions they are predisposed to have. It does not qualify to be a diagnosis in any manner, but their “qualitative genotyping” on the saliva samples the customer provides helps them predict ancestry, race, and ethnicity. They then utilize the information of their DNA fingerprinting and analysis to provide insight into what “clinically relevant variants” of various diseases might pose health risks. For instance, 23andMe states that most of its health reports for diseases and conditions are based on “a genetic model that includes customers’ results for thousands of genetic markers; variants found in many ethnicities.” These reports cover asthma, ADHD, depression, eczema, high blood pressure, type 2 diabetes, and skin cancer. Some of the reports are only provided for females, such as those covering PCOS and preeclampsia. More significantly however, some reports are specifically relevant to a person’s ethnicity: hereditary prostate cancer, for which they provide information on 1 variant (predominantly found in people of Northern European descent), and chronic kidney disease, with information on 2 variants (relevant to people of African descent). Finally, 23andMe’s Pharmacogenetics report also provides information from the DNA profile on how a person’s DNA can affect the way they process common medications for depression, heart attack, and cancer.

As mentioned previously, creating a DNA fingerprint and from it, a DNA profile requires cell samples from which DNA can be extracted and purified. Currently, the most common technique used is PCR. The father of genetic fingerprinting, Alec Jeffreys, initially developed an assay based on RFLP or Restriction Fragment Length Polymorphism. RFLP, which involves cutting DNA portions with “known variability,” can distinguish two individuals based on the DNA cutting patterns of the restriction enzymes that “digest” or cut the DNA. For a simple example, a normal DNA chromosome will produce two fragments when cut at the center, while a mutated chromosome might only produce one.

However, most of the distinguishability comes from being able to compare the sizes and shapes of the fragments produced, or whether the DNA is cut at all (as the presence of enzyme restriction sites depends on the DNA content itself). Although RFLP was used initially in forensic analysis, it has been replaced with PCR, as RFLP requires “large amounts of high-quality DNA” (Brittanica). With forensic DNA samples often easily degradable, hard to find (thus usually collected in small amounts), and collected postmortem, they are “subject to producing less-reliable results” through RFLP (Brittanica). With the expanded use of PCR now, many of the concerns and legal disputes around the validity and admissibility of DNA analysis in court have been reduced.

While RFLP is used less frequently than before in forensic analysis, it is still heavily used in genomic mapping and fingerprinting in the medical world. In the RFLP process, after DNA is first recovered from tissue, the restriction endonuclease enzyme cut the DNA into smaller pieces of various sizes. The DNA fragments are then separated by agarose gel electrophoresis, which uses an electric field to separate charged molecules into “bands.” How far across the bands move on the electrophoresis plate indicates how long the DNA pieces are. The DNA “band pattern” are then isolated and transferred onto a nylon membrane – this is also known as “southern blotting.” Radioactive or colored probes are added to view their positions via X-ray, making the pattern visible. This final DNA pattern becomes the DNA fingerprint. As mentioned before, DNA fingerprinting is used for many purposes: prenatal diagnosis, newborn screening, carrier screening, and of course forensic screening. We will later discuss the use of genetic testing and DNA fingerprinting for establishing family relationships and genealogy. For now, with each genetic signature decoded, we inch closer to a future where the complexities of our DNA are more understood, and the keys to our health and heritage are within our reach.

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