Double helix

Definition

A double helix is the structural formation of DNA, characterized by two long strands of nucleotides twisted around each other, resembling a spiral staircase. This unique structure enables the efficient storage of genetic information and is essential for the processes of replication and transcription, ultimately facilitating protein synthesis and inheritance.

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 the X-ray diffraction images produced by Rosalind Franklin.
2. Each strand of the double helix runs in opposite directions, known as antiparallel orientation, which is crucial for replication and enzyme binding.
3. The sugar-phosphate backbone forms the outer structure of the double helix, while the nitrogenous bases are located inside, protecting them from environmental damage.
4. Hydrogen bonds between paired bases provide stability to the double helix, allowing for both flexibility during replication and strength to maintain its structure.
5. The double helix's ability to unwind and separate is vital for processes like DNA replication and transcription, allowing access to genetic information.

Review Questions

• How does the structure of the double helix contribute to its function in storing genetic information?
  • The double helix structure allows for efficient packing of DNA within cells while also providing stability through its hydrogen bonds between paired bases. The twisted configuration protects the genetic code from damage and allows for easy access during replication and transcription. This structural design ensures that genetic information can be reliably stored and accurately copied when cells divide.
• Discuss how base pairing rules support the integrity of the double helix during DNA replication.
  • Base pairing rules dictate that adenine pairs with thymine and cytosine pairs with guanine, which is essential during DNA replication. As the double helix unwinds, each strand serves as a template for a new complementary strand based on these pairing rules. This specific pairing ensures that the genetic code is accurately copied and preserved across generations, maintaining the integrity of the organism's genetic information.
• Evaluate the significance of Rosalind Franklin's contributions to our understanding of the double helix structure in the context of modern genetics.
  • Rosalind Franklin's X-ray diffraction images provided critical evidence for the double helix model proposed by Watson and Crick. Her work highlighted not only the helical nature of DNA but also offered insights into its dimensions and molecular arrangement. Understanding this structure has paved the way for advancements in modern genetics, including genetic engineering, biotechnology, and our ability to manipulate DNA for medical and scientific purposes.

Related terms

nucleotide:

The basic building block of DNA, consisting of a phosphate group, a sugar molecule, 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.

DNA replication: The biological process of producing two identical replicas of DNA from one original DNA molecule, essential for cell division.