What significant structure of DNA did Watson and Crick reveal?

The significant structure of DNA that Watson and Crick revealed is the double helix structure. This discovery was groundbreaking because it provided a clear model for how DNA molecules are organized and how they function in the transmission of genetic information. The double helix comprises two strands of nucleotides twisted around each other, held together by base pairs. This model explained how genetic material could replicate and how traits are passed from one generation to the next.

The double helix structure also illuminated the mechanism of base pairing, where adenine pairs with thymine and cytosine pairs with guanine, forming the rungs of the helix. This base pairing is essential for the accurate replication of DNA during cell division and is fundamental to the process of protein synthesis.

Understanding the double helix not only transformed molecular biology but also laid the foundation for advances in genetics and biotechnology, fundamentally altering our understanding of life sciences. The other choices reflect incorrect forms of DNA; for instance, DNA is not a single helix, nor is it typically found in a triple helix or circular form in eukaryotic organisms. Circular DNA does occur in prokaryotes, such as bacteria, but it does not represent the canonical structure proposed by Watson and Crick.