The helical model for DNA given by Watson and Crick was

Options

A. B type right handed
B. Z type left handed
C. B type left handed
D. Z type right handed

Answer

To answer the question regarding the helical model for DNA proposed by Watson and Crick, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Structure of DNA**:
- Watson and Crick proposed that DNA is structured as a double helix. This means it consists of two strands that are twisted around each other.

2. **Identifying the Type of Helix**:
- The helical model described by Watson and Crick is specifically known as the B-type DNA, which is a right-handed helix. This means that if you were to follow the twist of the helix with your right hand, your thumb would point in the direction of the helix's twist.

3. **Base Pairing**:
- In the double helix, the strands are held together by base pairing. The bases pair specifically: adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). This base pairing is crucial for the stability of the DNA structure.

4. **Characteristics of B-DNA**:
- B-DNA is characterized as being wider and shorter compared to other forms of DNA, such as A-DNA and Z-DNA. It is the most common form of DNA found in cells.

5. **Conclusion**:
- Based on the information above, the correct answer to the question is that the helical model for DNA given by Watson and Crick was a **B type right-handed** helix.

### Final Answer:
The helical model for DNA given by Watson and Crick was **B type right-handed**.

---