These are due to the formation of two types of DNA binding sites within the octamer; the α1α1 site, which uses the α1 helix from two adjacent histones, and the L1L2 site formed by the L1 and L2 loops.
Isto débese á formación de dous tipos sitios de unión do ADN no octámero; o sitio α1α1 que usa a forma de hélice α1 de dúas histonas adxacentes e o sitio L1L2 formado polos bucles L1 e L2.