The Structure of DNA
Structure of DNA
DNA Components
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DNA (Deoxyribonucleic Acid) is a type of genetic material found in living organisms. It controls physical characteristics and cellular functions.
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The DNA molecule consists of two polynucleotide chains twisted around each other to form a double helix.
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Each polynucleotide chain is made up of nucleotide subunits.
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Nucleotides consist of a phosphate group, a deoxyribose sugar and a nitrogenous base.
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Four different nitrogenous bases exist in DNA: adenine (A), thymine (T), guanine (G), and cytosine (C).
Base Pairing and Bonding
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In DNA, bases pair in a specific manner: adenine pairs with thymine (A-T), and guanine pairs with cytosine (G-C). This is also known as complementary base pairing.
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Each base pair is held together by hydrogen bonds: Two between A-T and three between G-C.
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The phosphate group of one nucleotide binds to the deoxyribose sugar of the next nucleotide, forming a sugar-phosphate backbone. This is a result of a covalent bond, which are strong and stable.
Double Helix Structure
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The two polynucleotide chains run anti-parallel to each other, meaning they run in opposite directions.
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This double helix structure is twisted, creating major grooves and minor grooves.
Genome and Chromosomes
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The genetic information carried by an organism is its genome.
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This genome is divided into chromosomes, which are further divided into genes.
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Each gene has the instructions necessary for the production of a particular protein.
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Different species have different number of chromosomes. Humans have 46 (23 pairs).
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Each chromosome is a long, linear DNA molecule associated with proteins called histones. The DNA-histone complex is known as chromatin.
Remember, understanding the structure of DNA is fundamental to biology as it helps explain how genetic information is stored, transferred, and manifested as physical traits.