In one polyncleotide strand of a DNA molecule the ratio of `A+T//G+C` is `0.3`. What is the `A+G//T+C ` ratio of the entire DNA molecule ?

Options

A. 0.3
B. 0.6
C. 1.2
D. 1

Explanation

To solve the problem, we need to analyze the given information about the DNA molecule and apply Chargaff's rule.

### Step-by-Step Solution:

1. **Understanding the Given Ratio**:
We are given that the ratio of (A + T) / (G + C) = 0.3. This means that for every 0.3 units of (G + C), there are 1 unit of (A + T).

2. **Expressing in Terms of Variables**:
Let's denote:
- A + T = x
- G + C = y

From the given ratio, we can write:
\[ \frac{x}{y} = 0.3 \implies x = 0.3y \]

3. **Using Chargaff's Rule**:
According to Chargaff's rule, we know:
- A = T
- G = C

Therefore, we can express:
- A + G = A + T - T + G = x - T + G
- T + C = T + C = T + G

Since A = T and G = C, we can simplify:
- A + G = A + C (since G = C)
- T + C = T + C

4. **Finding A + G and T + C**:
Since A + T = x and G + C = y, we can also say:
- A + G = A + C = (A + T) + (G + C) - (T + C) = x + y - (T + C)

However, we can directly use the fact that:
\[ A + G = T + C \]
Therefore:
\[ A + G + T + C = x + y \]

5. **Calculating A + G / T + C**:
Since A + G = T + C, we can write:
\[ \frac{A + G}{T + C} = \frac{A + G}{A + G} = 1 \]

### Final Answer:
Thus, the ratio of (A + G) / (T + C) for the entire DNA molecule is **1**.