If a double-stranded DNA molecule is 22% G, what is the percentage of A, T, and C? Explain.

Question

Accepted Answer

All right. Hello everyone. So this question says that a student analyzed a double stranded DNA molecule and found that the DNA has 19% cytosine determine the percentage of G A and T and explain. So when it comes to questions like this, that are talking about the percentages of certain bases in a double stranded DNA strand, that's going to be in reference to Char Gas's rule. Because in char gas's rule, we can take advantage of the fact that base pairing is involved in double stranded DNA to find the percentages of each base in the strand itself. Because in double stranded DNA, right, the percentages of bases that pair together have to be equal to each other because they're pairing with each other, right? So when talking about base pairs recall that cytosine hydrogen bonds with guanine and adenine hydrogen bonds with thymine, this means that the percentages of cytosine and guanine must be equal and the percentages of adenine and thymine must be equal because these are the only four bases present in DNA. All of these percentages should equal 100%. So with that in mind, let's use the data that we're given Now, we're specifically told that we have 19% cytosine, which automatically means that we have to have 19% guanine because once again, these two bases are pairing with each other. So they should be present in equal amounts. So now 19 multiplied by two, excuse me, 19 multiplied by two equals 38%. So subtracting 100% by 38 is going to equal 62%. And so 62% of the DNA strand must be composed of adenine and thymine. These percentages are equal to each other for the individual basis. So 62% divided by two is going to equal 31% for both Adenine and Simon and there you have it. So now here we have our final answer which reads as follows. If the DNA sample has 19% cytosine, then it should have 19% guanine. Since cytosine and guanine are complementary, the sample also contains 31% Adenine and 31% thymine since Adenine and thymine are also complementary. And so with that being said, thank you so very much for watching and I hope we found this helpful.

If a double-stranded DNA molecule is 22% G, what is the percentage of A, T, and C? Explain.

Verified Solution

Key Concepts

Base Pairing Rules

Chargaff's Rules

Percentage Composition of DNA Bases