Double helix

Definition

The double helix is the structural configuration of DNA, consisting of two intertwined strands that resemble a twisted ladder. Each strand is composed of nucleotides, which include a sugar, phosphate group, and a nitrogenous base. The double helix structure allows for the stable storage of genetic information while providing mechanisms for replication and transcription.

5 Must Know Facts For Your Next Test

1. The double helix structure was first proposed by James Watson and Francis Crick in 1953, based on X-ray diffraction images taken by Rosalind Franklin.
2. Each turn of the double helix contains about 10 base pairs, contributing to its helical shape.
3. The two strands of the double helix are held together by hydrogen bonds formed between complementary nitrogenous bases.
4. The outer edges of the double helix are formed by the sugar-phosphate backbone, which provides structural support and stability.
5. The double helix not only encodes genetic information but also allows for easy unwinding during DNA replication and transcription processes.

Review Questions

• How does the structure of the double helix contribute to its function in storing genetic information?
  • The double helix structure provides a stable and compact arrangement for the storage of genetic information through its tightly coiled form. The pairing of complementary nitrogenous bases ensures accurate replication during cell division, while the antiparallel nature of the strands allows enzymes to access the DNA for transcription. This structure effectively safeguards genetic information while allowing it to be efficiently accessed when needed.
• What role does base pairing play in the stability of the double helix structure?
  • Base pairing is essential for maintaining the stability of the double helix structure by forming specific hydrogen bonds between complementary bases—adenine pairs with thymine and cytosine pairs with guanine. This specificity ensures that genetic information is accurately copied during replication and contributes to the overall stability of the DNA molecule. The consistency in base pairing also allows for reliable transmission of genetic information across generations.
• Evaluate how the discovery of the double helix structure impacted our understanding of molecular biology and genetics.
  • The discovery of the double helix structure revolutionized molecular biology by providing a clear model for how genetic information is stored and transmitted. It highlighted the importance of base pairing in replication and transcription processes, leading to advancements in understanding gene expression and regulation. This fundamental insight laid the groundwork for modern genetics, enabling significant developments in biotechnology, medicine, and evolutionary biology by revealing how heredity operates at a molecular level.

Related terms

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

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

Antiparallel Strands: The orientation of the two strands of the DNA double helix running in opposite directions, crucial for replication and enzyme interaction.