Overall, the analysis revealed 15 complex family trees unique to the Chernobyl population compared with the genomes of other dogs globally. One dog from Chernobyl City seems to have had recent run-ins with a Siberian huskie and a pinscher. The irradiated animals are most similar to German shepherds and Eastern European shepherds. The researchers compared the Chernobyl dog genomes to those of “free-breeding dogs” – aka mutts – from elsewhere, and also to genomes of 1,324 purebreds. Parent-offspring matings were the most common. Such homozygosity is a telltale sign of inbreeding. In addition, animals from the surrounding areas have more stretches of identical SNPs on both members of chromosome pairs than do other dogs. The dogs from the train station were the most adept at getting out and mingling, according to their SNPs. The data revealed three groups of dogs corresponding to the three geographic locations, but with enough overlap to suggest a canine version of cross pollination, what we geneticists dub “gene flow”. Novel gene variants among the animals were dubbed “survival loci” (a locus is the site of a gene on its chromosome). The researchers compared 129,497single-DNA-base sites in the genome that vary among individuals (SNPs) for 302 free-roaming Chernobyl dogs, and compared the data to those from other canine populations. The half-life exceeds 30 years, so the contamination will be around for awhile. For example, radiation in the power plant from the breakdown of cesium-137 is from 10 to 400 times higher than it is in Chernobyl City. Slavutych, 45 kilometers (28 miles) away in Belarus where most of the exposed families relocated.Chernobyl City about 15 kilometers (9.3 miles) away, where a few hundred people remain.The dense forest around the city of Pripyat, where many workers lived, about 3.5 km (2.2 miles) from the reactor.A train station in the midst of the contamination.The Chernobyl New Safe Confinement structure built to contain radioactivity from the damaged reactor. The researchers collected and preserved blood samples from dogs exposed to different radiation levels in several places: The Chernobyl Dog Research Initiative formed in 2017 to follow the ballooning canine population near the reactor remains – some 800 animals, for dogs don’t know they’re living in a hot zone and have no reason to flee as long as the workers continue to care for them. So far genetic studies of the nuclear exclusion zone have focused on vegetation, small animals, and genome changes in people who developed thyroid cancer following the exposure. Ultimately, new gene pools emerge from the population bottlenecks that winnow the survivors, with chance sampling favoring some gene variants (aka mutations) while eliminating others. Over time, natural selection favors mutations that provide a reproductive advantage in the new landscape, while weeding out non-adaptive traits. Genetic diversity declines rapidly in the face of forced inbreeding. Migration is severely constrained, and so animals trapped with their relatives mate with them, a little like the incest theme of the novels Flowers in the Attic and Middlesex. Reaction to the continuing exposure is at the population level too. With faulty DNA repair, mutations accrue. Damage to DNA from ionizing radiation ranges from single-DNA-base changes to shattered chromosomes, while heavy metal poisoning chops DNA across both strands and strangles repair. The area instantly became a genotoxic zone. Yes, Chernobyl was and remains a tourist destination, by jeep or jet. But some dogs survived, and the workers as well as tourists have cared for them since. Soon after the explosion, as humans fled, workers remained to clean up and to cull the canine population. The Chernobyl Dog Research Initiative has published their analysis of genetic changes among the dogs who live today in what researchers call the aftermath of “an ecological catastrophe of massive proportions.” Gabriella Spatola and Elaine Ostrander of the National Human Genome Research Institute and colleagues report their findings in Science Advances. The “nuclear exclusion zone” sounds similar, but is real, referring to the 3,004-square-kilometer (about 1,160-square-mile) environs of the Chernobyl nuclear power plant that exploded on April 26, 1986, at 1:23:58 am. In the original Planet of the Apes, the Forbidden Zone is a future radiation-devastated landscape from which hardy new mutants arise, shifting the evolutionary course of humanity.
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