Step 1: Introduction to DNA Structure.
The structure of DNA (Deoxyribonucleic Acid) was first described by Watson and Crick in 1953. They proposed a double helix model for the DNA molecule, which is now widely accepted as the standard model.
Step 2: Components of DNA.
DNA consists of two long chains of nucleotides coiled around each other to form the double helix. Each nucleotide is made up of:
1. A phosphate group
2. A deoxyribose sugar
3. A nitrogenous base (Adenine, Thymine, Cytosine, or Guanine).
The two strands of the helix are held together by hydrogen bonds between the nitrogenous bases, with adenine (A) pairing with thymine (T), and cytosine (C) pairing with guanine (G).
Step 3: The Double Helix Structure.
The two strands of DNA are anti-parallel, meaning one strand runs in a 5' to 3' direction and the other runs 3' to 5'. The double helix structure resembles a twisted ladder, with the sugar-phosphate backbone forming the sides of the ladder and the base pairs forming the rungs.
Step 4: Diagram (if applicable). (Include diagram of the double helical structure of DNA)
A diagram would show two intertwined strands with base pairs between them.
Step 5: Conclusion.
The double helical structure of DNA is crucial for its function in storing genetic information and facilitating replication.
Final Answer:
\[
\boxed{\text{DNA has a double helical structure with two strands connected by complementary base pairs.}}
\]
