DNA which is composed of dinucleotide unit is

Options

A. A-DNA
B. B-DNA
C. C-DNA
D. Z-DNA

Answer

To solve the question regarding which type of DNA is composed of dinucleotide units, we can follow these steps:

### Step 1: Understand the Structure of DNA
DNA (Deoxyribonucleic Acid) is primarily composed of nucleotides. Each nucleotide consists of three components: a phosphate group, a sugar (deoxyribose), and a nitrogenous base (adenine, thymine, cytosine, or guanine).

**Hint:** Recall the basic structure of nucleotides and the four nitrogenous bases that make up DNA.

### Step 2: Identify the Types of DNA
There are several forms of DNA, including:
- A-DNA
- B-DNA
- Z-DNA
- cDNA (complementary DNA)

**Hint:** Familiarize yourself with the different forms of DNA and their characteristics.

### Step 3: Focus on the Question
The question specifically asks for the type of DNA that is composed of dinucleotide units. A dinucleotide consists of two nucleotides linked together.

**Hint:** Think about which type of DNA might have a unique structure involving dinucleotide units.

### Step 4: Analyze the Options
Among the different types of DNA, Z-DNA is known to have a left-handed helical structure and is formed under certain physiological conditions. It is characterized by a repeating dinucleotide unit.

**Hint:** Consider the specific structural features that differentiate Z-DNA from other forms of DNA.

### Step 5: Conclusion
The correct answer to the question is Z-DNA, as it is the form of DNA that is composed of dinucleotide units.

**Final Answer:** Z-DNA

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