Although the experts agreed that it is an intriguing question, they highly doubted that a child’s DNA would change. “There shouldn’t be any way for someone to father someone else’s child,” reported Dr. Rezvani. After all, a donor’s blood cells should not create new sperm cells.
If sperm isn’t usually affected by transplants, why did Chris’s change? According to Mehrdad Abedi, the doctor who treated Chris, his semen change likely resulted from his vasectomy. The fact that sperm couldn’t move meant that their DNA would change.
If Chris hasn’t had a vasectomy, would the same result occur? We don’t know, and the scientists can’t test this on Chris. DNA analyses of sperm have shown the donor’s DNA instead of the patient’s before. Time will tell.
Human chimeras don’t only result from bone marrow transplants. For instance, there’s a case of a “vanishing twin,” where one fraternal embryo dies early on. The remaining embryo absorbs the twin’s DNA, resulting in two sets of DNA in the child.
During pregnancy, some women may retain some DNA from their baby. This phenomenon, called microchimerism, occurs in around 63% of women, even those over 94 years old. The New York Times says that microchimerism is “very common, if not universal.”
To make matters worse, it’s not easy to tell if someone is a chimera. In 2015, parents discovered that their newborn’s blood type and DNA did not match their parents’. They assumed that the clinic had used the wrong sperm.
Stanford geneticist Barry Starr recommended that the couple take a genetics test. Oddly, the test said that the father was the child’s uncle. “Human chimerism is very common, but exquisitely difficult to identify, coming to light almost exclusively by accidents like this,” biologist Charles Boklage told Buzzfeed News.
Chris’s case has changed many peoples’ opinions about DNA tests. Before, DNA tests were considered infallible in the courtroom. But the study suggests that common conditions may make DNA exams less foolproof than we assumed.
Chimeras have no issues in terms of health or medicine, but they create stumbling blocks for criminal investigators who rely on DNA tests to catch a perpetrator. With chimera cases coming to light, forensic scientists will have to redefine how they analyze DNA evidence.
Chris Long recovered from his AML. He is now healthy and experiences no issues as a chimera (he is completely innocent!) He told the Independent that he planned a trip to Germany to thank his donor for saving his life.
Chris has not reported whether or not he’ll continue working with the forensic scientists. However, Renee and her colleagues have suggested that they will continue to research the effects of chimerism — specifically how it affects a patient’s offspring.
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