if A=120 and C120, then a piece of DNA will have ______nucleotides.

Options

A. 240
B. 280
C. 480
D. data insufficient

Answer

To solve the question, we need to determine the total number of nucleotides in a piece of DNA given the number of adenine (A) and cytosine (C) bases.

### Step-by-Step Solution:

1. **Identify Given Values**:
- The number of adenine (A) bases is given as 120.
- The number of cytosine (C) bases is also given as 120.

2. **Apply Chargaff's Rule**:
- According to Chargaff's rule, in a double-stranded DNA molecule:
- The amount of adenine (A) is equal to the amount of thymine (T).
- The amount of cytosine (C) is equal to the amount of guanine (G).
- Therefore, if A = 120, then T must also be 120.
- Since C = 120, then G must also be 120.

3. **Calculate Total Nucleotides**:
- Now we can find the total number of nucleotides by adding the amounts of all four bases:
- Total nucleotides = A + T + C + G
- Total nucleotides = 120 (A) + 120 (T) + 120 (C) + 120 (G)
- Total nucleotides = 120 + 120 + 120 + 120 = 480

4. **Final Answer**:
- Therefore, a piece of DNA will have **480 nucleotides**.