▁that ▁are ▁essential ▁for ▁sister ▁chrom at id ▁coh es ion , ▁such ▁as ▁Sm c 3 ▁and ▁S cc 1 , ▁do ▁not ▁reg ulate ▁the ▁formation ▁of ▁c oval ent ▁b onds ▁between ▁coh es in ▁and ▁DNA , ▁indicating ▁that ▁DNA ▁interaction ▁is ▁not ▁sufficient ▁for ▁coh es ion . ▁In ▁addition , ▁disturb ing ▁the ▁ring ▁structure ▁of ▁coh es in ▁through ▁cle av age ▁of ▁Sm c 3 ▁or ▁S cc 1 ▁triggers ▁prem ature ▁sister ▁chrom at id ▁seg reg ation ▁in ▁v ivo . ▁This ▁shows ▁that ▁the ▁ring ▁structure ▁is ▁important ▁for ▁coh es in ’ s ▁function . ▁ ▁Early ▁studies ▁suggested ▁various ▁ways ▁in ▁which ▁coh es in ▁may ▁ent rap ▁DNA , ▁including ▁as ▁a ▁mon omer ▁that ▁holds ▁both ▁hom olog ues ▁together , ▁and ▁a ▁" hand - c uff " ▁model ▁where ▁two ▁inter tw ining ▁coh es in ▁complex es ▁each ▁hold ▁one ▁sister ▁chrom at id . ▁While ▁some ▁studies ▁support ▁the ▁idea ▁of ▁a ▁hand - c uff ▁model , ▁the ▁model ▁is ▁incons istent ▁with ▁a ▁number ▁of ▁experimental ▁observations , ▁and ▁is ▁generally ▁considered ▁to ▁ent rap ▁chrom atin ▁as ▁a ▁mon omer . ▁ ▁Even ▁though ▁the ▁ring ▁hypothesis ▁appears ▁to ▁be ▁valid , ▁there ▁are ▁still ▁questions ▁about ▁the ▁number ▁of ▁rings ▁required ▁to ▁hold ▁sister ▁chrom at ids ▁together . ▁One ▁possibility ▁is ▁that ▁one ▁ring ▁surr ounds ▁the ▁two ▁chrom at ids . ▁Another ▁possibility ▁involves ▁the ▁creation ▁of ▁a