Structure of DNA
DNA is a long double chain or duplex ‘molecule’ formed of millions of deoxyribonucleotides.DNA duplex has a diameter of 20 A.The duplex is coiled plectonemically in a right handed manner just as rope stair is twisted to form a spiral.this coiling produces alternate major and minor grooves.
The structure of DNA (Deoxyribonucleic Acid) is often described as a double helix. This structure, proposed by James Watson and Francis Crick in 1953, is made up of two long strands of nucleotides that coil around each other, resembling a twisted ladder.
Here’s a breakdown of the DNA structure:
1. Nucleotides:
DNA is composed of repeating units called nucleotides. Each nucleotide consists of three components:
- Phosphate group (PO₄³⁻)
- Deoxyribose sugar (a five-carbon sugar)
- Nitrogenous base (Adenine (A), Thymine (T), Cytosine (C), Guanine (G))
2. Double Helix:
The two strands of DNA run in opposite directions (antiparallel) and twist around each other to form a helical structure.
3. Base Pairing:
- Adenine (A) pairs with Thymine (T) via two hydrogen bonds.
- Cytosine (C) pairs with Guanine (G) via three hydrogen bonds. This complementary base pairing is key to DNA’s replication process and stability.
4. Sugar-Phosphate Backbone:
The sugar and phosphate groups of nucleotides form the backbone of the DNA strand, linked by phosphodiester bonds. This backbone provides structural support and stability.
5. Antiparallel Orientation:
The two strands of DNA run in opposite directions: one strand runs in the 5′ to 3′ direction (5-prime to 3-prime), and the other runs 3′ to 5′.
6. Major and Minor Grooves:
The twisting of the double helix creates major and minor grooves, which are important for protein binding and the regulation of genetic expression.
This intricate structure allows DNA to store genetic information, replicate during cell division, and direct protein synthesis through transcription and translation.
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