2020托福听力练习：蛋白质测试补充DNA分析（下载）

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　　DNA analysis is a staple of crime scenes—and crime shows, like HBO's The Night of or the old standby, CSI:

　　"We just need to get this to the DNA lab, confirm it's the victim's blood. And then, case closed."

　　And it's not just for crime: DNA sequencing also helps determine our relationship to Neandertals, and our primate cousins.

　　Problem is, DNA's a relatively fragile molecule—it doesn't last forever. What's more sturdy is protein. So now researchers have come up with a way to use protein in a similar way to DNA: to link an individual to a piece of evidence or to determine ethnic background.

　　The protein source these scientists studied was human hair, from 76 individuals of European-American, African-American and Kenyan descent. And they determined that the variation of a couple hundred proteins in a person's hair could be enough to single her out from a group of one million individuals.

　　The way it works is that proteins are made according to the instructions in DNA. So one individual's genetic variations can result in slightly different proteins being made, compared to another individual. And by determining the protein composition, the scientists can then extrapolate info about the DNA. The results are in the journal PLoS ONE.

　　The researchers say the technique still is not ready for prime-time—ideally the process needs to be more sensitive, to avoid consuming valuable crime scene or archaeological samples in the analysis. And the statistics behind the technique need to be validated, too. But someday, they say, it could come within a hair of DNA analysis.