In a strand of DNA, if the percentage of thymine is 30%, what would the percentage of cytosine in the same DNA strand be?

20%

Explanation:

I haven't learned this exactly yet, but if there is 30% of thymine, then there has to be 30% of adenine because they match. That would leave 40% for other Guanine and Cytosine, and since they also match that means that it is exactly half, meaning that there is 20% Guanine and 20% Cytosine.

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