Mark the incorrect statement for DNA.

Options

A. The ratios between Adenine and Thymine and Guanine and Cytosine are constant and equal to one in dsDNA.
B. DNA is an acidic substance present in the nucleus was first identified by Friedrich Meischer in 1869.
C. The X - ray diffraction data was used for discovery of the DNA
D. Two strands are anti- parallel to each other.

Answer

To determine the incorrect statement regarding DNA, we will analyze each option provided in the question step by step.

### Step-by-Step Solution:

1. **Evaluate the first statement**: "The ratio between adenine and thymine and guanine and cytosine are constant and equal to 1 in double-stranded DNA."
- In double-stranded DNA, adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). According to Chargaff's rules, the amount of A is equal to T, and the amount of G is equal to C. Therefore, this statement is **correct**.

2. **Evaluate the second statement**: "DNA is an acidic substance present in the nucleus and was first identified by Friedrich Mischer in 1869."
- DNA is indeed an acidic molecule due to its phosphate backbone, and it was first discovered by Friedrich Mischer in 1869. Thus, this statement is also **correct**.

3. **Evaluate the third statement**: "X-ray diffraction data was used for the discovery of DNA."
- This statement is **incorrect**. While X-ray diffraction was crucial in understanding the structure of DNA (not its discovery), it was not used to discover DNA itself. The famous X-ray diffraction image known as Photo 51, produced by Rosalind Franklin, helped elucidate the helical structure of DNA, but it did not lead to the discovery of DNA as a molecule.

4. **Evaluate the fourth statement**: "Two strands are anti-parallel to each other."
- In DNA, the two strands run in opposite directions, meaning one strand runs from the 5' to 3' direction while the other runs from 3' to 5'. This anti-parallel arrangement is a fundamental characteristic of DNA structure, making this statement **correct**.

### Conclusion:
The incorrect statement among the options provided is the third statement: "X-ray diffraction data was used for the discovery of DNA."

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