Double helix

Definition

A double helix is the structural formation of DNA, where two long strands of nucleotides twist around each other, resembling a twisted ladder. This unique shape is crucial for the stability and functionality of DNA, allowing it to store genetic information and replicate accurately during cell division.

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 the work of Rosalind Franklin and Maurice Wilkins.
2. Each strand of the double helix is made up of a sugar-phosphate backbone, with nitrogenous bases attached to the sugars forming the rungs of the ladder.
3. The anti-parallel orientation of the two strands, where one runs 5' to 3' and the other runs 3' to 5', is essential for the replication process.
4. The double helix can unwind and separate during DNA replication, allowing each strand to serve as a template for synthesizing a new complementary strand.
5. Mutations can occur in the DNA sequence, which can be identified through changes in the structure of the double helix that affect base pairing.

Review Questions

• How does the structure of the double helix contribute to its function in genetic information storage and transmission?
  • The double helix structure allows DNA to pack efficiently into chromosomes while maintaining stability. The complementary base pairing ensures that genetic information is accurately replicated and transmitted during cell division. Additionally, the twisting shape protects the genetic code from damage and provides a mechanism for controlled access during processes like transcription and replication.
• Discuss how base pairing within the double helix structure affects the accuracy of DNA replication.
  • Base pairing within the double helix structure is critical for maintaining genetic fidelity during replication. The specific pairing between adenine and thymine, and between cytosine and guanine, ensures that each strand can serve as an accurate template for creating a new complementary strand. This precise matching reduces the likelihood of errors during DNA synthesis, contributing to overall genomic stability.
• Evaluate the implications of mutations in the double helix structure on protein synthesis and overall cellular function.
  • Mutations in the double helix can lead to alterations in the DNA sequence that may result in changes to mRNA transcription and subsequent protein synthesis. Depending on their nature, these mutations can have varying effects on cellular function, ranging from benign to harmful. For example, if a mutation alters a codon in a gene, it could produce a malfunctioning protein or disrupt regulatory pathways, ultimately impacting cellular health and contributing to diseases like cancer.

Related terms

Nucleotide: The building blocks of DNA and RNA, consisting of a sugar, a 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.

Replication fork: The Y-shaped region that forms during DNA replication where the double helix unwinds and separates into two single strands.