(problem 9) what is an insulator? a protein that blocks rna polymerase from interacting with a promoter a special type of histone that occurs at the boundaries of genes a transcriptional repressor protein that surrounds the telomeres and centromeres a sequence of dna that inhibits the action of enhancers in a position-dependent manner a segment of dna that forms supercoiled heterochromatin that is devoid of any dna-regulator binding

There are two correct answers:
1. A sequence of DNA that inhibits the action of enhancers in a position-dependent manner. Those are enhancer-blocking insulators and when an insulator is located in between a promoter and an enhancer, it prevents the influence of the enhancer on the promoter.

2. A segment of DNA that forms supercoiled heterochromatin that is devoid of any DNA-regulator binding. Those are barrier insulators and they prevent euchromatin (transcriptionally active region) from turning into heterochromatin (transcriptionally inactive).