DNA, or deoxyribonucleic acid, is a molecule composed of two long strands that coil around each other to form a double helix. The primary components of DNA are:
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Nucleotides: The building blocks of DNA, each nucleotide consists of three parts:
- A phosphate group: This consists of a phosphorus atom bonded to four oxygen atoms. It connects the nucleotides together in a strand.
- A sugar molecule: Specifically, deoxyribose, which is a five-carbon sugar. This sugar differs from ribose (the sugar found in RNA) by lacking one oxygen atom.
- A nitrogenous base: There are four types of nitrogenous bases in DNA:
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
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Base Pairing: The nitrogenous bases pair specifically: adenine pairs with thymine (A-T), and cytosine pairs with guanine (C-G). This complementary base pairing is essential for DNA replication and the transmission of genetic information.
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Double Helix Structure: The two strands of DNA run in opposite directions (antiparallel) and are held together by hydrogen bonds between the paired bases. The sugar and phosphate form the backbone of the DNA strand, while the bases project inward, forming the steps of the helical ladder.
Together, these components allow DNA to store genetic information, replicate itself, and govern the synthesis of proteins, which are crucial for the functioning of living organisms.