You’ve seen it on TV. Crime scene investigators ____1____ what might be a murder scene. There are blood ____2____ — but no body. Who’s the victim? Now, a new technique developed in the Netherlands might help real-world investigators establish the age of the victim using only blood. The research was published in the journal Current Biology.
Usually, age is determined by physical characteristics, such as teeth or bones. Great—if you have a body. Researchers have tried unsuccessfully to use blood. But in this study, the scientists used immune cells called T-cells. T-cells ____3____ receptors that match molecules on bacteria, viruses, even tumors. The cellular activity that produces these receptors also produces a type of circular DNA molecule as a by-product.
The number of these receptor by-products declines regularly over time. So scientists devised a test to measure the molecules — and use that to infer someone’s age based on his or her blood. The results appear to ____4____ nine years. So forensic scientists could use a bloodstain to ____5____ a victim’s age to ____6____ two decades. That’s a big range—but it could help solve crimes when the victims can’t be found.
【视听版科学小组荣誉出品】
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CSI：仅用血迹估测受害者年龄 你一定在电视上看到过这样的画面：在凶案现场总会出现犯罪现场调查员的身影。现场四处血污，但是并无尸体。那么到底谁是受害者呢？如今，根据《当代生物学》刊登的研究结果，一项在荷兰研究而成的新技术或许可以帮助现实世界的调查人员利用血迹来确定受害者的年龄。 通常情况下，年龄是通过人的身体外表特征，如牙齿或骨骼，来测定的。这当然再好不过了——只要你尸骨仍存。研究人员一直尝试利用血液测定年龄，但未曾成功。不过在这项研究中，科学家们利用了一种被称为T细胞的免疫细胞。T细胞通过受体来识别外来入侵物，这些受体会抵御细菌、病毒、甚至是肿瘤分子。而产生这些受体的细胞活性也会制造副产品——一种环状DNA分子。 随着时间的推移，这些受体副产品的数量会逐渐下降。据此，科学家们设计了一种测试方法来检测分子，并利用它以某人的血液来推断其年龄，测定结果能精确到上下9年内。这样，法医可以利用血迹是受害者的年龄范围缩小到20年以内。这个范围很大——但在受害者失踪的情况下会有利于破案。