1. DNA: This is the genetic material itself, containing the instructions for building and maintaining an organism.

2. Proteins: These are essential for the structure and function of chromosomes. They serve several roles:

* Histones: These are proteins that DNA wraps around to form nucleosomes, the basic units of chromatin. This packaging helps to condense the long DNA molecule and make it more manageable within the nucleus.

* Non-histone proteins: These proteins are involved in a variety of functions related to chromosome structure, replication, and gene expression. Examples include:

* Scaffold proteins: They help to organize and maintain the overall shape of chromosomes.

* Replication proteins: They help to copy DNA during cell division.

* Transcription factors: These proteins bind to DNA and regulate the expression of genes.

* Repair proteins: These proteins help to repair damaged DNA.

So, while DNA is the primary component, proteins are essential partners in forming and maintaining chromosomes. They provide the structural framework, help with DNA organization and replication, and regulate gene expression.