Here's why:

* Chromosomes: These are long, thread-like structures found in the nucleus of every cell. They are made up of DNA tightly coiled around proteins.

* DNA: Deoxyribonucleic acid is the molecule that carries the genetic instructions for building and maintaining an organism. It's a double helix structure, and the sequence of its building blocks (nucleotides) determines the instructions.

* Uniqueness: Each individual (except for identical twins) has a unique sequence of DNA within their chromosomes. This sequence is inherited from their parents and determines traits like eye color, hair color, and even predisposition to certain diseases.

So, to summarize:

* Chromosome contains the DNA which holds the unique genetic instructions for an individual.