Here, purines form hydrogen bonds to pyrimidines, with A bonding only to T, and C bonding only to G.. 
other structures can also be formed, with the central set of four bases coming from either a single strand gúnwe around the bases, or several different at Stds, each oòrùnting one base to the central Structure.In addition to these stacked structures, télọ̀me also form large loop structures called telomere loops, or t-loops.. 