DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for all living organisms. It's made of two linked strands that wind around each other to resemble a twisted ladder—a shape known as a double helix.
Each strand is made up of nucleotides, which are the building blocks of DNA. Each nucleotide consists of three parts:
- A phosphate group
- A sugar group (deoxyribose)
- One of four nitrogenous bases:
- Adenine (A)
- Thymine (T)
- Guanine (G)
- Cytosine (C)
These nucleotides are linked together covalently, forming a sugar-phosphate backbone with the bases extending outwards. The sequence of these bases along the backbone encodes genetic information.
The two strands of DNA are held together by hydrogen bonds between the bases. Adenine always pairs with thymine (A-T), and guanine always pairs with cytosine (G-C). This complementary base pairing is crucial for the replication and transcription of DNA.
In summary, DNA is made of two strands of nucleotides, which are linked together by a sugar-phosphate backbone and held together by hydrogen bonds between complementary base pairs.
