Unique structures known as telomeres—protective structures composed of DNA—are found at the end of eukaryotic chromosomes (eukaryotes are organisms with cells that contain complex structures). Experiments have determined that without telomeres, the chromosome structure could be damaged; the DNA of the chromosome tends to stick to other pieces of DNA, and enzymes (deoxyribonucleases) are more likely to degrade or digest the ends of the chromosomes.