Human genes are made up of deoxyribonucleic acid (DNA). Here's a breakdown of its structure:

1. The Building Blocks:

* Nucleotides: DNA is made up of long chains of molecules called nucleotides. Each nucleotide has three parts:

* Sugar: A deoxyribose sugar molecule.

* Phosphate Group: A negatively charged phosphate group.

* Nitrogenous Base: One of four nitrogen-containing bases:

* Adenine (A)

* Thymine (T)

* Guanine (G)

* Cytosine (C)

2. The Double Helix:

* Pairing: DNA exists as a double helix, two strands of nucleotides intertwined like a twisted ladder. The bases from each strand pair up specifically:

* Adenine (A) always pairs with Thymine (T)

* Guanine (G) always pairs with Cytosine (C)

* Hydrogen Bonds: These base pairs are held together by weak hydrogen bonds.

* Sugar-Phosphate Backbone: The sugar and phosphate groups of each nucleotide form the backbone of the DNA strand, running along the outside of the helix.

3. The Genetic Code:

* Sequence: The order of the nucleotides in a DNA sequence is what carries the genetic information, or code.

* Genes: Specific segments of DNA that contain the instructions for building proteins or regulating other biological processes are called genes.

In summary:

Human genes are segments of DNA, which is a double helix made of nucleotides. The sequence of these nucleotides within a gene determines the instructions for building proteins and other important molecules. This information is what makes each individual unique!