Double helix

Definition

A double helix is the structural formation of DNA, consisting of two intertwined strands that coil around each other, resembling a twisted ladder. This unique structure is essential for the stability and functionality of DNA, allowing it to store genetic information and facilitating processes such as replication and transcription.

5 Must Know Facts For Your Next Test

1. The double helix structure was first described by James Watson and Francis Crick in 1953, based on X-ray diffraction images taken by Rosalind Franklin.
2. The two strands of the double helix are held together by hydrogen bonds between paired nitrogenous bases, which are critical for maintaining the DNA structure.
3. The double helix is crucial for DNA replication, as the strands can separate, allowing each original strand to serve as a template for new complementary strands.
4. The shape of the double helix influences how DNA interacts with proteins, affecting gene expression and regulation.
5. In addition to DNA, some forms of RNA can also adopt a helical structure, but most RNA molecules are single-stranded.

Review Questions

• How does the structure of the double helix facilitate DNA replication?
  • The double helix structure allows the two strands of DNA to unwind and separate during replication. Each original strand serves as a template for synthesizing new complementary strands. This separation is essential because it enables enzymes like DNA polymerase to accurately copy the genetic information, ensuring that each daughter cell receives an identical copy of the DNA.
• Compare and contrast the double helix structure of DNA with the structure of RNA.
  • The double helix is specific to DNA, which consists of two intertwined strands, while RNA typically exists as a single-stranded molecule. However, both nucleic acids are composed of nucleotides with similar components. The presence of uracil in RNA instead of thymine and ribose sugar instead of deoxyribose distinguishes RNA from DNA. While DNA's double helix provides stability for long-term genetic storage, RNA's single-stranded nature allows for diverse functions in protein synthesis and gene regulation.
• Evaluate the significance of Watson and Crick's discovery of the double helix structure for molecular biology.
  • Watson and Crick's discovery of the double helix was revolutionary for molecular biology as it provided a clear model explaining how genetic information is stored and transmitted. Understanding this structure laid the groundwork for later research on genetic coding, inheritance patterns, and mechanisms like replication and transcription. Their work highlighted the relationship between structure and function in biological molecules, influencing fields such as genetics, biotechnology, and medicine by enabling advancements in genetic engineering and understanding hereditary diseases.

Related terms

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

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

Antiparallel: Refers to the orientation of the two strands of DNA in a double helix, where one strand runs in the 5' to 3' direction and the other runs in the opposite direction.