How does the structure of DNA identified by Watson and Crick differ from the model previously proposed by Linus Pauling and others?

The structure of DNA identified by James Watson and Francis Crick significantly differs from the model previously proposed by Linus Pauling and others. Here's how:

1. Shape: Pauling proposed a triple helix model for DNA, where three chains of DNA were coiled around each other. Watson and Crick, on the other hand, proposed a double helix structure, where two chains of DNA wind around each other.

2. Location of Bases: In Pauling's model, the bases were on the outside of the DNA molecule, and the phosphates were in the core. However, Watson and Crick's model proposed that the bases were in the core of the molecule, and the phosphates were on the outside.

3. Base Pairing: Pauling's model did not include specific base pairing, while Watson and Crick's model proposed that adenine (A) always pairs with thymine (T), and cytosine (C) always pairs with guanine (G). This base pairing is crucial for DNA replication.

4. Hydrogen Bonding: Watson and Crick's model also included hydrogen bonding between the bases, which was not part of Pauling's model. These hydrogen bonds help to stabilize the DNA molecule.

5. Directionality: In Watson and Crick's model, the two strands of DNA run in opposite directions (antiparallel), which was not the case in Pauling's model.

In conclusion, Watson and Crick's model of DNA was more accurate and detailed, and it provided a mechanism for DNA replication, which Pauling's model did not.