2021年考研真题2021年考研英语真题和答案(10)

and supports businesses that offer to search for a

family’s geographic roots .Most

tests require collecting cells by webbing saliva in

the mouth and sending it to the pany for testing.All tests require a potential candidate with whom to pare DNA.But some observers are skeptical, “There is a kind

of false precision being hawked by people claiming they

are doing an cestry testing,” says Trey Duster, a New

York University sociologist.He

notes that each individual has many ancestors-numbering in the hundreds just a few centuries back.Yet most ancestry testing only considers a single lineage, either the Y chromosome inherited through men in a

father’s line or mitochondrial DNA, which a passed down only from mothers.This

DNA can reveal geic information about only one or two ancestors, even though, for exle, just three generations back people also have six other great-grandparents or,

four generations back,

14 other great-great-grandparents.Critics

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