Because it takes three units where there's only four choices at each position to have at least 20 unique combinations.

因为每个位点上仅有四种可能性,只有采用三个碱基一组,才能取得至少二十种不同的组合方式

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There are 64 combinations of three bases and I only need to describe 20, so there's combinations to spare.

三个一组的碱基产生六十四种组合,而我只需对应二十种氨基酸,所以一种氨基酸会对应不同密码子

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How many combinations of codons are there if there's three bases and four possibilities at each base?

那密码子的组合方式到底有几种呢,三个位点,每个位点四种选择

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