To put it simply, chromosomes are important because they contain the entire (or at least the vast majority of) genetic information for an organism. The organism's DNA is contained within the chromosome as a long series of nucleotides that are organized into genes. Each chromosome has thousands of gene DNA sequences that are organized into chromosomal structures through the help of different proteins. Chromosomes are organized by these proteins into very compact structures called chromatin that can fit into the nucleus of a cell. These chromosomal proteins also help aid the DNA of the cell undergo different functions such as replication for cell division and unwinding different genes for use in protein synthesis.