dna in a chromosome consists of . noncoding, repetitive dna is found in of chromosomes; these structures play important roles during replication. chromatin is a complex of dna and protein; roughly is dna, and is evenly divided between histone and nonhistone proteins. the five types of contain a preponderance of the basic, positively charged amino acids , which help neutralize and stabilize the negatively charged dna double helix. four histones associate to form the core of the . are a broad category that includes hundreds to thousands of different proteins with a variety of functions. one nonhistone protein that acts as an enzyme is , which is crucial to replication.