Question

question 8
1 pts
if a dna sample contains 33% thymine, what percentage of the sample is guanine?
50%
33%
66%
34%
17%

Explanation:

Step1: Recall DNA base pairing

In DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). So, the percentage of A equals T, and G equals C.

Step2: Calculate percentage of A and T combined

Given thymine (T) is 33%, so adenine (A) is also 33%. The combined percentage of A and T is \( 33\% + 33\% = 66\% \).

Step3: Calculate percentage of G and C combined

The total percentage of all bases in DNA is 100%. So, the combined percentage of guanine (G) and cytosine (C) is \( 100\% - 66\% = 34\% \).

Step4: Calculate percentage of guanine (G)

Since G = C, we divide the combined percentage of G and C by 2. So, \( \frac{34\%}{2} = 17\% \). Wait, no, wait. Wait, earlier step: Wait, 100 - 66 is 34, but G and C are equal, so G is 17? Wait, no, wait, I made a mistake. Wait, T is 33, so A is 33. So A+T=66. Then G+C=34. So G is 17? But wait, the options have 17% as an option. Wait, but let me recheck. Wait, DNA base pairing: A=T, G=C. So if T is 33, A is 33. So A+T=66. Then G+C=34. So G is 17, C is 17. So the percentage of guanine is 17%? Wait, but the options include 17%. Wait, but let me check again. Wait, maybe I miscalculated. Wait, 100 - (33*2) = 100 - 66 = 34. Then G is 34/2 = 17. Yes. So the percentage of guanine is 17%.

Answer:

17% (the option with 17%)