Short DNA segment has 80 thymine and 90 guanine bases. The total number of nucleotides are

Options

A. 160
B. 40
C. 80
D. 340

Answer

To solve the question about the total number of nucleotides in a DNA segment with 80 thymine (T) and 90 guanine (G) bases, we will apply Chargaff's rules. Here’s a step-by-step breakdown of the solution:

### Step-by-Step Solution:

1. **Identify the Given Information:**
- Number of Thymine (T) bases = 80
- Number of Guanine (G) bases = 90

2. **Apply Chargaff's Rules:**
- According to Chargaff's rules, in double-stranded DNA:
- 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, since there are 80 T bases, there must also be 80 A bases.
- Since there are 90 G bases, there must also be 90 C bases.

3. **Calculate the Total Number of Nucleotides:**
- Total nucleotides = Number of Adenine (A) + Number of Thymine (T) + Number of Guanine (G) + Number of Cytosine (C)
- Substitute the values:
- Total nucleotides = 80 (A) + 80 (T) + 90 (G) + 90 (C)
- Total nucleotides = 80 + 80 + 90 + 90 = 340

4. **Final Answer:**
- The total number of nucleotides in the DNA segment is **340**.