Double helix

Definition

The double helix is the structural form of DNA, consisting of two intertwined strands that resemble a twisted ladder. Each strand is composed of a backbone made of sugar and phosphate groups, with nitrogenous bases attached to the sugars forming the rungs of the ladder. This unique structure allows for the efficient storage and replication of genetic information, playing a critical role in how organisms inherit traits.

5 Must Know Facts For Your Next Test

1. The double helix was first described by James Watson and Francis Crick in 1953, based on earlier research by Rosalind Franklin and Maurice Wilkins.
2. Each complete turn of the double helix measures about 10 base pairs in length.
3. The antiparallel nature of the double helix means that the two strands run in opposite directions, which is essential for replication and function.
4. Hydrogen bonds between complementary base pairs help stabilize the double helix structure while allowing it to unwind during DNA replication.
5. The double helix's shape is critical for its ability to package DNA efficiently within the nucleus of eukaryotic cells.

Review Questions

• How does the structure of the double helix contribute to its function in genetic information storage?
  • The double helix structure contributes to genetic information storage by allowing for compact organization within cells. The twisted shape enables long strands of DNA to fit neatly inside the nucleus, while the complementary base pairing ensures that information can be accurately replicated. Additionally, the stable yet flexible structure allows for necessary interactions with proteins involved in gene expression and replication.
• What role do hydrogen bonds play in maintaining the stability of the double helix?
  • Hydrogen bonds play a vital role in maintaining the stability of the double helix by forming connections between complementary nitrogenous bases on opposite strands. Specifically, adenine forms two hydrogen bonds with thymine, while guanine forms three with cytosine. This bonding not only stabilizes the structure but also allows the strands to separate during processes like replication and transcription, making it possible for genetic information to be accessed when needed.
• Evaluate the significance of Watson and Crick's discovery of the double helix structure on our understanding of genetics.
  • Watson and Crick's discovery of the double helix structure fundamentally changed our understanding of genetics by providing a clear model for how genetic information is stored and transmitted. Their work revealed how base pairing allows for precise replication, which is crucial for inheritance. This insight laid the groundwork for molecular biology as a field, influencing countless studies in genetics, biotechnology, and medicine, ultimately leading to advances such as gene editing and personalized medicine.

Related terms

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

Base Pairing: The specific pairing of nitrogenous bases (adenine with thymine and guanine with cytosine) that stabilizes the double helix structure.

DNA Replication: The process by which DNA makes a copy of itself before cell division, ensuring genetic information is passed on to daughter cells.