Here's a breakdown:

Nucleotides are composed of three parts:

1. A phosphate group: A molecule containing phosphorus and oxygen.

2. A sugar molecule:

* In DNA, the sugar is deoxyribose.

* In RNA, the sugar is ribose.

3. A nitrogenous base: There are five different nitrogenous bases found in DNA and RNA:

* Adenine (A)

* Guanine (G)

* Cytosine (C)

* Thymine (T) – Found only in DNA

* Uracil (U) – Found only in RNA

Key Differences:

* Sugar: DNA uses deoxyribose, while RNA uses ribose.

* Base: DNA uses thymine (T), while RNA uses uracil (U).

How Nucleotides Build DNA and RNA:

* Nucleotides link together to form long chains called polynucleotides.

* In DNA, two polynucleotide chains twist around each other to form a double helix.

* In RNA, a single polynucleotide chain forms a helix.

The sequence of nucleotides in DNA and RNA determines the genetic information they carry.