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段落1

This is Scientific American 60-Second Science. I'm Karen Hopkin. This'll just take a minute.

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Nothing says summer like a sweet ear of corn.

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But that treat would be much harder to eat if it weren't for a crucial mutation.

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The change, in just one letter of the DNA code, appears to have cracked the hard casing that covered every kernel in corn's wild ancestor.

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That's according to a study in the journal Genetics.

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Corn was domesticated from a wild grass called teosinte some 9,000 years ago.

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But how did our ancestors make maize the agricultural marvel it is today?

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Seems they selectively propagated plants with a particular mutation, one that made the kernels more accessible to hungry Homo sapiens.

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The researchers compared the DNA of 16 varieties of modern corn and 20 types of teosinte.

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And they found a single, key mutation that is present in modern corn but absent in its wild-grass ancestor.

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This genetic hiccup disrupts the activity of a protein called tga1.

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In teosinte, the tga1 protein directs the formation of a hard shell around every corn kernel.

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But the modern maize mutation gives tga1 a new set of marching orders.

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The mutant protein turns the ear inside out, converting the seed cases into a cob that holds all the kernels in place.

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When the researchers reversed the effects of the mutant protein, the ancestral seed-case remnants started to reappear.

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The results suggest that even minor genetic changes can lead to some pretty tasty developments.

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You might call it a-maize-ing.

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But that would be corny.

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Thanks for the minute, for Scientific American 60-Second Science. I'm Karen Hopkin.

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