In a single strand from a DNA molecule, nucleotides are linked by covalent bonds between :

Options

A. sugar and phosphate groups
B. sugar and nitrogenous bases
C. phosphate groups and nitrogenous bases
D. nitrogenous bases

Explanation

To answer the question, "In a single strand from a DNA molecule, nucleotides are linked by covalent bonds between:", we need to understand the structure of a nucleotide and how they are connected in a DNA strand.

### Step-by-Step Solution:

1. **Understanding Nucleotides**:
- A nucleotide consists of three components: a sugar molecule (deoxyribose in DNA), a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, or guanine).

2. **Formation of Nucleotides**:
- The sugar and the phosphate group form the backbone of the DNA strand. The nitrogenous base is attached to the sugar.

3. **Linking Nucleotides**:
- In a single strand of DNA, nucleotides are linked together through covalent bonds. Specifically, the phosphate group of one nucleotide forms a bond with the sugar of the next nucleotide.

4. **Type of Covalent Bond**:
- The specific type of covalent bond that links the phosphate group of one nucleotide to the sugar of the next nucleotide is called a **phosphodiester bond**. This bond is formed through an ester linkage between the phosphate and the hydroxyl group of the sugar.

5. **Conclusion**:
- Therefore, in a single strand of DNA, nucleotides are linked by covalent bonds between the phosphate group of one nucleotide and the sugar of the next nucleotide, forming phosphodiester bonds.

### Final Answer:
Nucleotides in a single strand of DNA are linked by covalent bonds between the phosphate group of one nucleotide and the sugar of the next nucleotide, forming **phosphodiester bonds**.

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