The ratio of phosphates, sugars and nitrogen bases in ds-DNA

Options

A. `1:2:1`
B. `1:1:1`
C. `1:1:2`
D. `3:1:1`

Answer

To determine the ratio of phosphates, sugars, and nitrogen bases in double-stranded DNA (ds-DNA), we can break down the components of DNA and analyze their relationships.

### Step-by-Step Solution:

1. **Understanding the Structure of DNA**:
- DNA is composed of nucleotides, which are the building blocks of DNA.
- Each nucleotide consists of three components: a phosphate group, a deoxyribose sugar, and a nitrogenous base.

2. **Identifying Components**:
- In ds-DNA, each nucleotide contains:
- **1 phosphate group**
- **1 deoxyribose sugar**
- **1 nitrogenous base** (which can be adenine, thymine, cytosine, or guanine)

3. **Counting the Ratios**:
- For every nucleotide in the DNA strand, there is exactly:
- 1 phosphate
- 1 sugar
- 1 nitrogen base
- Therefore, if we consider a single nucleotide, the ratio of phosphates to sugars to nitrogen bases is:
- Phosphate: 1
- Sugar: 1
- Nitrogen base: 1

4. **Final Ratio**:
- Thus, the overall ratio of phosphates to sugars to nitrogen bases in ds-DNA is:
- **1:1:1**

5. **Conclusion**:
- The correct answer to the question is **1:1:1**.