Here's a breakdown:

* DNA (Deoxyribonucleic Acid): The fundamental molecule of heredity. It's a long, complex chain that contains the instructions for building and maintaining an organism.

* Genes: Segments of DNA that code for specific traits, like eye color or hair texture.

* Alleles: Different versions of the same gene. They occupy the same location (locus) on a chromosome. For example, there might be an allele for blue eyes and an allele for brown eyes.

So, to put it simply: Alleles are variations of a gene, and they are made up of a specific sequence of DNA nucleotides.