Praxis II: Biology Content Knowledge Exam Prep

Answer: B, The statement about the Watson-Crick model of DNA that is untrue is that the two strands of DNA run in parallel directions. The strands are actually said to antiparallel, one strand runs in the 5’ to 3’ direction, and the other runs in the 3’ to 5’ direction.

Key Takeaway: The Watson-Crick model of DNA explains the structure of DNA. In the model, DNA was correctly proposed to be arranged in a double helix consisting of two strands that are antiparallel to one another. In the model, adenine is paired with guanine, and cytosine is paired with guanine. Both pairings are maintained by hydrogen bonding, which allows the structure to maintain its helical formation. The structure also predicted how DNA replication could occur, as the double helix would need to uncoil before replication could proceed.