Which of the following equalities is not true for double-stran...

Question

Which of the following equalities is not true for double-stranded DNA?

(G+A)=(C+T)

Accepted Answer

Hi, everyone. Welcome back. Let's look at our next question as per Char Gaffs rule, which of the following choices is correct. Choice. A number of C equals number of TT in DNA. Choice B, number of T equals number of G and DNA choice C amount of in parentheses. A plus G equals amount of in parentheses, T plus C. And finally, choice D both option A and B. Well, as we can recall both looking at our answer choices and from our content video char Gaff's rule has to do with the relative amount of different nucleotides in a DNA molecule. So there's two parts of that rule. And the first has to do with the complementary basis saying that the number of C nucleotides must equal the number of G nucleotides and the number of A nucleotides must equal the number of T nucleotides that led scientists to the discovery of the fact that these complementary bases existed in pairs always in the same amount. But that allows us to rule out choices A and B because they're arranged incorrectly. A says number of C equals number of T and that's not correct. C and G exist in the same amounts. And choice B says number of T equals number of G and that's also incorrect since the number of T should equal the number of a bases in a DNA molecule. And so choice D both option A and B, it's also obviously incorrect. So we're left with just one answer. Choice C that the amount of A plus G must equal the amount of T plus C. And this is correct because as we look at our two complementary two pairs of complementary bases that exist in equal amounts. The second part says that the amount of purines and the amount of pines are present in a ratio of 1 to 1. And our purines are A and G A and guanine, our per are C and T I always have a hard time remembering that a good little trick is that the pyrimidines, pyrimidine has A Y and cytosine and thymine are the two bases with Ys in them. So that's an easy way to remember that. But so indeed are pines A and G must be in a 1 to 1 ratio with our prime means. So the amount of A plus G together must equal the amount of T plus C together. So that makes C our correct answer as per car char graphs rule which of the following choices is correct choice C, the amount of A plus G must equal the amount of T plus C. See you in the next video.

Which of the following equalities is not true for double-stranded DNA?
(G+A)=(C+T)

Key Concepts

Base Pairing Rules

Chargaff's Rules

DNA Composition

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