chromosomes
The nucleus is a membrane-enclosed organelle found in most eukaryotic cells. The nucleus is the largest organelle in the cell and contains most of the cell's genetic information mitochondria also contain DNA, called mitochondrial DNA, but it makes up just a small percentage of the cells overall DNA content . The genetic information, which contains the information for the structure and function of the organism, is found encoded in DNA in the form of genes. A gene is a short segment of DNA that contains information to encode an RNA molecule or a protein strand. DNA in the nucleus is organized in long linear strands that are attached to different proteins. These proteins help the DNA to coil up for better storage in the nucleus. Think how a string gets tightly coiled up if you twist one end while holding the other end. These long strands of coiled-up DNA and proteins are called chromosomes. Each chromosome contains many genes. Humans have about 20,000 to 22,000 genes scattered among 23 chromosomes.