Which of the following equations are true for the percentages ...

Question

Which of the following equations are true for the percentages of nucleotides in double-stranded DNA?

(A)/(G)=(T)(C)

Accepted Answer

Hi, everyone. Let's take a look at this practice problem together. Which of the following shows the correct formula. The answer options are a open parentheses. Adenine plus thymine closed parentheses equals open parentheses. Cytosine plus guanine closed parentheses. Option B open parentheses. Adenine minus thymine, closed parentheses equals open parentheses. Cytosine minus guanine closed parentheses. Option C open parentheses. Adenine plus guanine closed parentheses equals open parentheses. Thymine plus cytosine closed parentheses and D all options are correct. So the question is asking us to determine how the number of nucleotides is balanced and we will be able to solve this by recalling tar gas rule. And what was his role? Recall that the rule is about complementary base pairing. It states that adenine is always bonded to thymine and guanine is always bonded to cytosine. This means that the percentage of adenine is equal to the percentage of thymine and the percentage of guanine is equal to the percentage of cytosine, we can eliminate. Option B because we know that there is no subtraction of nucleotides occurring. So to understand this further, let's take a look at an example, let's say in a DNA sample, we know that all the bases added together. So adenine plus thymine, plus cytosine plus guanine has to equal 100%. So let's say that we have 30% uh they need, that means there is 30% thymine. And we know that because of Char Gaff's role. Now, if we add the 30% plus 30% this equals 60% of the sample is either adenine or thymine. So in our sample of the 100% 60% is adenine or thymine. That means there's 40% left. And since the percentage of guanine is always equivalent to the percentage of cytosine, that means they each represent 20% of the total sample. So 20% and 20% cytosine. If we did the formula for option A, that would be 30% adenine plus 30% thymine equals 20% cytosine plus 20% guanine. And that is not a correct and balanced formula. So option A is incorrect. The correct formula is option C. So for our example, that would be 30% adenine plus 20% guanine equals 30% thine plus 20% cytosine. So the correct answer is option C open parentheses. Adenine plus guanine, closed parentheses equals open parentheses. Thymine plus cytosine, closed parentheses. All right, everyone. I hope you found this helpful and I'll see you soon for the next practice problem.

Which of the following equations are true for the percentages of nucleotides in double-stranded DNA?
(A)/(G)=(T)(C)

Key Concepts

Chargaff's Rules

Base Pairing

Nucleotide Composition

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