1. Deoxyribose sugar: This is the same for all four nucleotides.
2. Phosphate group: This is also the same for all four nucleotides.
3. Nitrogenous base: This is the part that varies and gives each nucleotide its unique identity.
Here's a breakdown of the four nitrogenous bases:
* Adenine (A): A double-ringed purine base. It pairs with thymine (T) through two hydrogen bonds.
* Guanine (G): Another double-ringed purine base. It pairs with cytosine (C) through three hydrogen bonds.
* Thymine (T): A single-ringed pyrimidine base. It pairs with adenine (A) through two hydrogen bonds.
* Cytosine (C): A single-ringed pyrimidine base. It pairs with guanine (G) through three hydrogen bonds.
In summary:
* Adenine and guanine are purines (double-ringed structures).
* Thymine and cytosine are pyrimidines (single-ringed structures).
* Adenine always pairs with thymine, and guanine always pairs with cytosine.
This specific pairing pattern, known as complementary base pairing, is crucial for the structure and function of DNA. It ensures that the two strands of DNA are held together by hydrogen bonds and that the genetic information is replicated accurately.
