The table below shows the percentages of bases in a DNA sample. How much Guanine (G) should you expect to find in the sample? a 17% b 33% c 50% d 83%

Answer 1

In DNA, the bases pair in a specific way: adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). According to Chargaff's rules, the percentages of A and T are equal, and the percentages of G and C are equal.

If we have the percentage of one base, we can deduce the percentages of the others.

Given the options, let's denote the percentage of Guanine (G) as $x$. According to Chargaff’s rules:

1. If we know the percentage of cytosine (C), it will also be $x$ (because G and C are equal).
2. The percentages of adenine (A) and thymine (T) will total $100$.

If we analyze the provided percentages:

• If 17% is $G+C$, then $2x=17$ → $x=8.5$
• If 33% is $G+C$, then $2x=33$ → $x=16.5$
• If 50% is $G+C$, then $2x=50$ → $x=25$
• If 83% is $G+C$, then $2x=83$ → $x=41.5$

Since we don’t have the exact percentage of another base, we cannot directly calculate exactly how much G should be present. If you have the percentage for one base (like A, T, or C), then we could find G using its paired base.

Given that the percentages listed are not sufficient to conclude definitively without knowing more about the total composition, it's likely that the answer requires more information on either A, T, or C.

If you know the composition of A and T or C, we can apply the rules to find G. Alternatively, if you're looking for any of the provided options based on expectations, more detail is required, like any base mentioned in the question or overall totals to guide a specific answer. If no additional data is given, we cannot definitively assume one of the choices as correct based on just base pair rules.