What are the highly condensed portion of chromatin which appear as very dark areas in an transmission electron micrograph

An allosteric transcription regulator called HisP regulates the enzymes for histidine biosynthesis in the bacterium E.coli histidine modulates HisP activity. On binding histidine , HisP alters its conformation, markedly changing its affinity for the regulatory sequences in the promoters of the genes for the histidine biosynthetic enzymes.

A if HisP function as a gene repressor, would you expect that hisP would bind more tightly or less tightly to the regulatory sequence when histidine is abundant? describe your answer.

B if HisP functions as a gene activator, would you expect that HisP would bind more tightly or less tightly to the regulatory sequences when histidine levels are low ? describe your answer.