Double helix

Definition

A double helix is a molecular structure formed by two strands of nucleotides wound around each other, resembling a twisted ladder. This iconic shape is crucial for the stability and function of DNA, as it allows for the efficient storage and transmission of genetic information while also enabling replication and repair mechanisms.

5 Must Know Facts For Your Next Test

1. The double helix structure was first described by James Watson and Francis Crick in 1953, building on X-ray diffraction data obtained by Rosalind Franklin.
2. The two strands of the double helix are antiparallel, meaning they run in opposite directions, which is vital for replication and enzyme activity.
3. The sugar-phosphate backbone of each strand provides structural stability, while the nitrogenous bases face inward, forming base pairs that hold the strands together.
4. In crystallography, understanding the double helix is essential for elucidating the structures of DNA and RNA, which are often studied using techniques like X-ray crystallography.
5. The double helix model not only explains how genetic information is stored but also how it is accurately copied during cell division, ensuring genetic continuity.

Review Questions

• How does the double helix structure facilitate the functions of DNA?
  • The double helix structure of DNA supports its functions by providing a stable yet flexible framework for storing genetic information. The antiparallel arrangement of the two strands allows for efficient base pairing through complementary nucleotides, which is critical during DNA replication. Additionally, this twisted shape protects the genetic code from environmental damage while allowing access to enzymes that read and replicate DNA.
• Discuss the significance of base pairing in maintaining the integrity of the double helix structure.
  • Base pairing is fundamental to the integrity of the double helix because it ensures that each strand can serve as a template for replication. The specific pairing of adenine with thymine and cytosine with guanine stabilizes the structure through hydrogen bonds. This specificity not only preserves genetic information but also facilitates accurate copying during cell division, reducing mutations and errors in genetic material.
• Evaluate how advancements in crystallography have enhanced our understanding of the double helix and its implications in genetics.
  • Advancements in crystallography have greatly improved our understanding of the double helix by allowing scientists to visualize its three-dimensional structure at atomic resolution. Techniques such as X-ray crystallography have revealed intricate details about how nucleic acids interact with proteins and small molecules, influencing gene expression and regulation. This knowledge has implications in genetics, biotechnology, and medicine, aiding in drug design and therapies targeting genetic disorders.

Related terms

Nucleotide: The basic building block of nucleic acids, composed of a nitrogenous base, a sugar molecule, and a phosphate group.

Base Pairing: The specific hydrogen bonding between nitrogenous bases in DNA, where adenine pairs with thymine and cytosine pairs with guanine, facilitating the double helix structure.

Crystallography: A technique used to study the atomic structure of crystals, including nucleic acids and viruses, by analyzing the patterns produced when X-rays are diffracted through them.