What does it mean to speak of bases as being complementary?

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Accepted Answer

Alright, hello everyone. So this question says true or false. When two bases have the same amount, they are complementary bases. Option A says true and option B says false. So very quickly, this particular question is talking about complementary base pairing and the subsequent ratios of complementary bases in a given sample of DNA. So because of that, this has to do with Char GFS rules. So let's just briefly talk about what that means, right, Chargaff rules named after the scientist Chargaff is essentially talking about the ratios of complementary base pairs in double stranded DNA specifically because when Char GV was observing DNA of different species, one thing was very clear, right? It was clear that Adenine and Thiamine were present in equal amounts and cytosine and guanine were also present in equal amounts, namely or importantly, right, these two base pairs are complementary base pairs because we know that they hydrogen bond in double stranded DNA. And so later, it's Char G's rule that led to a further understanding of what DNA looks like. That's how we understood it to be a double strand with those complementary base pairings in the middle. And so that right, there is what leads us to the problem with the statement that we're given because as mentioned before, right to graph's rules apply to double stranded DNA. The reason why proportions are equal among complementary bases is because the amount of adenines in one base, for example, should pair with all of the thymine's in the complementary base or in the complementary strand I should say. But when talking about single stranded DNA, that doesn't have to be true, right? Because in single stranded DNA, we're not observing any base pairing. And so the ratios of these bases to each other doesn't necessarily matter. So the statement that we're given as it's written in the question has to be false. The only way that the statement can be true is if it specifies that we're talking about double stranded DNA because it's only when talking about double stranded DNA that we see these equal proportions of our complimentary basis because of that base pairing. So the answer here is going to be option B because the statement is false. And so with that being said, thank you so very much for watching. And I hope you found this helpful.

What does it mean to speak of bases as being complementary?

Verified video answer for a similar problem:

Key Concepts

Complementary Bases

Base Pairing Rules

Genetic Complementarity