Chargaff' a rule states that in an organism:

Options

A. amount of adenine (A) is equal to that of cytosine (C) and the amount of thymine (T) is
B. amounts of all bases are equal
C. amount of adenine (A) is equal to that of thymine (T) and the amount of guanine (G) is equal to that of cytosine (C)
D. amount of adenine (A) is equal to that of guanine (G) and the amount of thymine (T) is equal to that of cytosine (C)

Explanation

**Step-by-Step Solution:**

1. **Understanding Chargaff's Rule**: Chargaff's rule states that in any given organism, 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). This can be summarized as:
- A = T
- G = C

2. **Identifying Base Pairing**: The rule emphasizes the complementary nature of the DNA bases:
- Adenine pairs with Thymine (A-T)
- Guanine pairs with Cytosine (G-C)

3. **Analyzing the Statements**: We need to evaluate the given statements based on Chargaff's rule:
- **Statement 1**: "Amount of adenine is equal to cytosine."
- This is incorrect because according to Chargaff's rule, A is equal to T, not C.
- **Statement 2**: "Amount of all bases are equal."
- This is also incorrect. While A = T and G = C, it does not mean that A = G or that all bases are equal.
- **Statement 3**: "Amount of adenine is equal to thymine and the amount of guanine is equal to the amount of cytosine."
- This statement is correct as it directly reflects Chargaff's rule.
- **Statement 4**: "Amount of adenine is equal to guanine."
- This is incorrect because A is not equal to G.

4. **Conclusion**: The only correct statement according to Chargaff's rule is the third one: "Amount of adenine is equal to thymine and the amount of guanine is equal to the amount of cytosine."

**Final Answer**: The correct statement according to Chargaff's rule is: "Amount of adenine is equal to thymine and the amount of guanine is equal to the amount of cytosine."

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