The average Guanine content in yeast is found to be 18%.
Which of the following represents the nitrogenous base content percentages correctly from the above data?

Options

A. A: 18%, T: 18%, C: 36%
B. A: 36%, T: 32%, C: 32%
C. A: 32%, T: 32%, C: 18%
D. A:18%, T: 18%, C:18%

Answer

To solve the problem regarding the nitrogenous base content percentages in yeast, we will apply Chargaff's rules, which state that in DNA, the amount of adenine (A) is equal to the amount of thymine (T), and the amount of guanine (G) is equal to the amount of cytosine (C).

### Step-by-Step Solution:

1. **Identify the given information**:
- The average guanine (G) content in yeast is given as 18%.

2. **Apply Chargaff's Rule**:
- According to Chargaff's rule, the amount of guanine (G) is equal to the amount of cytosine (C). Therefore, if G = 18%, then C must also be 18%.

3. **Determine adenine (A) and thymine (T) content**:
- Since A = T, we need to find the total percentage of A and T.
- The total percentage of all nitrogenous bases must equal 100%.
- We already have G = 18% and C = 18%.
- Therefore, the combined percentage of G and C is 18% + 18% = 36%.

4. **Calculate the remaining percentage for A and T**:
- Total percentage of A and T = 100% - (G + C) = 100% - 36% = 64%.

5. **Distribute the remaining percentage equally between A and T**:
- Since A = T, we divide the remaining percentage by 2.
- A = T = 64% / 2 = 32%.

6. **Summarize the nitrogenous base content percentages**:
- Adenine (A) = 32%
- Thymine (T) = 32%
- Guanine (G) = 18%
- Cytosine (C) = 18%

7. **Select the correct option**:
- The correct representation of the nitrogenous base content percentages is:
- Adenine (A) = 32%
- Thymine (T) = 32%
- Guanine (G) = 18%
- Cytosine (C) = 18%
- This matches with option C.

### Final Answer:
The correct representation of the nitrogenous base content percentages is:
- Adenine (A) = 32%
- Thymine (T) = 32%
- Guanine (G) = 18%
- Cytosine (C) = 18%