Exploring the Safety of DNA Testing: Uncovering Chimerism Risks
Written on
Understanding Genetic Testing Errors
What does it signify when a patient’s genetic testing yields unexpected or incorrect results? This scenario unfolded for a Boston mother in her 50s, who, after seeking a kidney transplant, learned that two of her three adult sons were not biologically related to her. Despite having given birth and raised them, the test results suggested otherwise, leading to perplexity and concern.
To uncover the truth, medical professionals delved into the family’s medical history, pondering whether a hospital mix-up had occurred during birth—a highly improbable event given the rarity of such occurrences.
Meanwhile, across the country in Washington State, a woman applying for state aid faced fraud accusations when genetic tests revealed that her third child was not biologically hers, despite her other two children qualifying for assistance. A medical professional was present at the birth for immediate genetic verification, but once again, the test results contradicted her claims.
In California, a father seeking confirmation of his children’s paternity was astonished to discover that the tests indicated he was not their biological parent. These baffling results prompt an exploration of the phenomenon known as chimerism.
The Enigma of Chimerism
In Greek mythology, the Chimera was a fearsome creature composed of different animal parts. This concept of hybrid beings has fascinated humans for centuries. Modern science reveals that chimerism can occur when genetic material from multiple sources merges, either accidentally or through intentional processes.
For example, gardeners may graft plant parts together to enhance survival and productivity. Similarly, human chimeras can arise during early development when one fraternal twin is absorbed by the other, resulting in individuals with two distinct DNA sets.
Can Humans Be Chimeras?
Yes, humans can indeed be chimeras, although the prevalence of this condition is not well-known as it often goes undetected. Scientific literature documents around 100 cases of chimerism in humans. The aforementioned scenarios likely involve individuals who were once fraternal twins but ended up with two genetic makeups.
This condition, termed "tetragametic chimerism," results from the absorption of one twin into the other during gestation. Furthermore, modern medicine can create chimeras through procedures such as organ transplants where the recipient may carry the donor’s DNA.
How Common Is Chimerism?
According to the National Society of Genetic Counselors (NSGC), many individuals with chimerism remain undiagnosed. They estimate that 20 to 30 percent of singleton pregnancies may originally stem from multiple embryos, suggesting that tetragametic chimerism could be more widespread than current data indicates.
The NSGC notes that most individuals with this condition do not face health issues, but a diagnosis can provide clarity about unexplained circumstances.
The Implications of Chimerism
In popular media, DNA evidence is often presented as infallible; however, cases exist where police have mistakenly ruled out suspects due to chimeric DNA results. This raises fundamental questions about identity and the uniqueness of our genetic codes.
Some scientific literature suggests that individuals with noticeable differences in pigmentation or eye color might have a higher likelihood of being chimeras. Moreover, children conceived through in vitro fertilization (IVF) may have an increased chance of being chimeric.
What Lies Ahead?
In the U.S., approximately twenty individuals die daily waiting for organ transplants, prompting scientists to explore cross-species DNA experiments. The closer the genetic relationship between species, the more successful the fusion; for instance, rat DNA has been used to assist in organ development in mice.
Recent experiments in China combined human DNA with monkey embryos, though the majority of these embryos did not survive. This research raises ethical questions about the potential of creating human-animal chimeras, as portrayed in the fictional narrative of “The Island of Dr. Moreau.”
Ethical Considerations
The ethics of using animals for organ harvesting or medical testing is contentious, and concerns about potential zoonotic diseases loom large. Researchers are investigating ways to minimize the risks associated with creating chimeras, but the ethical implications remain complex and often divided.
As science progresses, will ethical guidelines keep pace with new capabilities? Different countries may adopt varying stances on permissible research, and consensus on ethical boundaries appears elusive.
In a paper published by the International Society For Stem Cell Research, authors candidly stated, “Science will not sit idle,” underscoring the urgency of addressing these ethical dilemmas.
This video discusses the safety of DNA testing and the implications of genetic genealogy, providing insights into the complexities surrounding such tests.
In this TEDx talk, Matt Artz explores the safety concerns associated with DNA testing, shedding light on potential risks and misconceptions.
Sources used in preparing this article: Daily Beast, European Journal of Medical Genetics, Insider.com, International Society For Stem Cell Research, Journal of Law and Biosciences, National Society of Genetic Counselors, Nature, New England Journal of Medicine, New Scientist, Scientific American, Stanford Medicine — Department of Genetics, The Guardian and Wikipedia.
© 2022 L. E. Langner. All rights reserved.