Here are the essential concepts you must grasp in order to answer the question correctly.
Base Pairing Rules
In DNA, the base pairing rules dictate that adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). This means that the amount of adenine in a DNA molecule is equal to the amount of thymine, while the amount of guanine is equal to the amount of cytosine. Understanding these rules is essential for determining the proportions of the different bases in a DNA sample.
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Chargaff's Rules
Chargaff's rules state that in any given DNA molecule, the amount of adenine is equal to thymine, and the amount of guanine is equal to cytosine. This principle helps in predicting the composition of DNA based on the known percentages of one or more bases. In this case, knowing that 30% of the nucleotides are adenine allows us to infer the percentage of guanine based on these rules.
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Percentage Calculation in DNA Composition
To calculate the percentage of guanine when given the percentage of adenine, one must consider the total percentage of the four bases (A, T, G, C) must equal 100%. If 30% is adenine, then 30% must also be thymine, leaving 40% for guanine and cytosine combined. Since guanine and cytosine are equal, this means guanine must account for 20% of the total nucleotides.
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