Chromosomes are composed of DNA and:

Chromosomes are the organized structures of genetic material found within the nucleus of eukaryotic cells. They are primarily composed of DNA and specialized proteins [1]. The DNA molecule, which carries the hereditary information for an organism, is extremely long and must be tightly packaged to fit inside the microscopic nucleus [1]. This packaging is achieved by wrapping the DNA around positively charged proteins called histones, forming complexes known as nucleosomes [2]. These nucleosomes further fold into chromatin fibers [1]. In addition to histones, chromosomes contain a diverse group of non-histone proteins that assist in structural maintenance, DNA replication, and gene expression [2]. While lipids and carbohydrates are essential cellular components found in the cytoplasm and cell membranes, they are not structural constituents of chromosomes [3].

Sources

1. [1] http://www.nature.com/scitable/topicpage/dna-packaging-nucleosomes-and-chromatin-310
2. [2] https://www.ncbi.nlm.nih.gov/books/NBK9863/
3. [3] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Activity 2.3: Let us investigate > p. 12