Chromosome with DNA computer artwork Chromosomes are the structures in cells that carry the DNA deoxyribonucleic acid genetic material DNA exists as a double helix with two sugarphosphate strands yellow spiralling round each other linked by the interactions between bases red and blue between them The sequence of bases encodes a recipe for making a specific protein Chromosomes normally exist as long strands but condense into Xshaped structures such as this during cell division Each chromosome comprises two identical chromatids linked at the centromere During replication the chromatids separate to become two new identical chromosomes