DNA quadruplex, molecular model. This dimeric quadruplex of DNA (deoxyribonucleic acid) is thought to form as part of telomeres, the structures at the end of chromosomes that are thought to play a role in ageing. This quadruplex (four-part complex) is formed from an oligonucleotide, a short strand of DNA, held together by hydrogen bonding of its guanine nucleotide bases. Two strands within the DNA are highlighted in pink and green.