Previous research suggests these genes evolved in response to millions of years of retrovirusinfection.
先前的研究表明,这些基因是宿主与逆转录病毒感染百万年斗争的进化结果。
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KoRV (koala retrovirus) integrates itself into the animalsa DNA, and may be passed on genetically as well as through direct infection, experts have found, though they are unsure how it is spread.