Question

coding for traits practice
1 multiple choice 1 point
if a dna strand contains 20% adenine, how much guanine is present?
25%
10%
20%
30%

Explanation:

Step1: Recall Chargaff's rules

In DNA, \(A = T\) (adenine pairs with thymine) and \(G = C\) (guanine pairs with cytosine). So \(A+T + G + C=100\%\). Given \(A = 20\%\), then \(T = 20\%\).

Step2: Calculate \(G + C\)

\(A+T=20\% + 20\%=40\%\). So \(G + C=100\%-(A + T)=100\% - 40\% = 60\%\).

Step3: Find \(G\)

Since \(G = C\), then \(G=\frac{G + C}{2}=\frac{60\%}{2}=30\%\)

Answer:

30%