Question

The table below shows the percentages of bases in a DNA sample. How much Adenine (A) should you expect to find in the sample?
Base
% of Total DNA
A
C 17
G
T 33
O a
• b
0 c
O d
17%
33%
50%
72%

Answer 1

To solve for the percentage of Adenine (A) in the DNA sample, we can use the fact that in double-stranded DNA, the amount of Adenine (A) is equal to the amount of Thymine (T), and Cytosine (C) is equal to Guanine (G).

The percentages of bases are typically represented as follows:
- A = % of Adenine
- T = % of Thymine
- C = % of Cytosine
- G = % of Guanine

From the table you provided, we know the following:
- % of C = 17%
- % of T = 33%

Since A pairs with T, the percentage of A can be calculated as follows:

1. The total number of bases must sum to 100%. Therefore:
\[
A + T + C + G = 100\%
\]

2. Substituting the known values into the equation:
\[
A + 33\% + 17\% + G = 100\%
\]

3. Simplifying the equation:
\[
A + G + 50\% = 100\%
\]
\[
A + G = 50\%
\]

4. Since C = G (17%), we can set G = 17%:
\[
A + 17\% = 50\%
\]

5. Solving for A gives:
\[
A = 50\% - 17\%
\]
\[
A = 33\%
\]

Thus, in the given DNA sample, you should expect to find **33% Adenine (A)**.