Double helix

Definition

The double helix is the structure of DNA, consisting of two long strands that wind around each other, resembling a twisted ladder. This iconic shape is essential for DNA's ability to store genetic information and play a crucial role in replication and transcription processes. The complementary base pairing between the two strands ensures accurate genetic information transfer 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, using data from Rosalind Franklin's X-ray diffraction images.
2. Each strand of the double helix runs in opposite directions, which is referred to as antiparallel orientation, allowing for proper base pairing.
3. The sugar-phosphate backbone of each DNA strand forms the sides of the ladder, while the paired nitrogenous bases form the rungs.
4. The stability of the double helix is maintained through hydrogen bonds between the base pairs and covalent bonds within the sugar-phosphate backbone.
5. During DNA replication, the double helix unwinds, and each original strand serves as a template for synthesizing new complementary strands.

Review Questions

• How does the structure of the double helix contribute to its function in storing genetic information?
  • The double helix structure allows DNA to efficiently store vast amounts of genetic information due to its compact and stable form. The specific pairing of nitrogenous bases enables accurate replication and transcription, ensuring that the genetic code can be reliably passed on during cell division. This structure also allows for the regulation of gene expression, as certain regions can be easily accessed or tightly wound based on cellular needs.
• Discuss the implications of the double helix structure for the process of DNA replication.
  • The double helix's unique structure facilitates DNA replication by allowing each strand to serve as a template for synthesizing new strands. As the double helix unwinds, enzymes like DNA polymerase can access each original strand, adding complementary nucleotides to form new strands. This semi-conservative replication method ensures that each daughter cell receives an exact copy of the genetic material, maintaining genetic continuity across generations.
• Evaluate how advancements in understanding the double helix structure have influenced modern genetics and biotechnology.
  • Understanding the double helix has revolutionized modern genetics and biotechnology by providing insight into how genetic information is stored, replicated, and expressed. This knowledge has paved the way for techniques such as PCR (polymerase chain reaction), gene editing (like CRISPR), and genetic engineering. The ability to manipulate DNA sequences has vast applications in medicine, agriculture, and forensic science, enabling breakthroughs in disease treatment, crop improvement, and criminal investigations.

Related terms

Nucleotide: The basic building block 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.

DNA Polymerase: An enzyme that plays a key role in DNA replication by adding nucleotides to a growing DNA strand complementary to the template strand.