Which of the following is an incorrect statement with regard to DNA?

Options

A. The two strands of DNA helix are antiparallel
B. The two strands are held together by glycosidic bond between bases
C. Sugar and phosphate form the backbone of DNA
D. There are 10 base pairs in one turn of helical B-DNA

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for an incorrect statement regarding DNA. To answer this, we need to evaluate each provided statement about DNA.

2. **Reviewing the DNA Structure**: Recall that DNA is a double helix structure composed of two strands that run in opposite directions (anti-parallel). Each strand is made of a sugar-phosphate backbone with nitrogenous bases attached.

3. **Evaluating the Statements**:
- **Statement 1**: The DNA model proposed by Watson and Crick is based on X-ray diffraction data. This is true; their model was indeed based on the work of Rosalind Franklin and Maurice Wilkins.
- **Statement 2**: Two strands are held together by glycosidic bonds. This is incorrect. The strands are held together by hydrogen bonds between the nitrogenous bases, not glycosidic bonds. Glycosidic bonds connect the sugar to the nitrogenous base within a single nucleotide.
- **Statement 3**: Sugar and phosphate form the backbone of DNA. This is true; the sugar-phosphate backbone is a fundamental part of the DNA structure.
- **Statement 4**: There are ten bases in one turn of the helical B-DNA. This is also true; B-DNA has approximately 10 base pairs per helical turn.

4. **Identifying the Incorrect Statement**: From the evaluation, Statement 2 is the only incorrect statement regarding DNA.

5. **Final Answer**: Therefore, the answer to the question is that the incorrect statement is the one that claims two strands are held together by glycosidic bonds.