Which term describes the structure of DNA as a spiral ladder?

Which term describes the structure of DNA as a spiral ladder?

• A. Single-stranded helix
• B. Complex helix
• C. Double-stranded helix
• D. Triple-stranded helix

Answer: (C)

The structure of DNA is best described as a double-stranded helix, which means it consists of two long strands of nucleotides twisted around each other, forming a spiral shape reminiscent of a twisted ladder. This key feature is crucial as it accounts for DNA's ability to store genetic information effectively. Each strand is composed of a backbone made of sugar and phosphate groups, with pairs of nitrogenous bases connecting the two strands in the center, resembling the rungs of a ladder. The specificity of base pairing (adenine with thymine and cytosine with guanine) is fundamental to DNA replication and the transmission of genetic information, allowing the strands to remain complementary. In contrast, a single-stranded helix would imply only one strand of nucleotides, which does not reflect the true structure of DNA. The terms "complex helix" and "triple-stranded helix" also do not accurately describe what is commonly known about DNA, which is specifically established as a double helix based on Watson and Crick's foundational model. The double-stranded nature is integral to its stability and function in cellular processes.

The structure of DNA is best described as a double-stranded helix, which means it consists of two long strands of nucleotides twisted around each other, forming a spiral shape reminiscent of a twisted ladder. This key feature is crucial as it accounts for DNA's ability to store genetic information effectively.

Each strand is composed of a backbone made of sugar and phosphate groups, with pairs of nitrogenous bases connecting the two strands in the center, resembling the rungs of a ladder. The specificity of base pairing (adenine with thymine and cytosine with guanine) is fundamental to DNA replication and the transmission of genetic information, allowing the strands to remain complementary.

In contrast, a single-stranded helix would imply only one strand of nucleotides, which does not reflect the true structure of DNA. The terms "complex helix" and "triple-stranded helix" also do not accurately describe what is commonly known about DNA, which is specifically established as a double helix based on Watson and Crick's foundational model. The double-stranded nature is integral to its stability and function in cellular processes.