Transcription when Chromosomes are Condensed
The compaction of DNA into chromatin is a very complex process that involves not only DNA, but on the histone code. Some may say that the histone code plays more of a role in chromatin state To develop a screen you would have understand the act of methylation, acetylation, ubiquitination, and phosphorylation of all modifiable histone residues. The modification of histone residues determine if the chromatin is in a heterochromatin or euchromatin state and even in which sections of DNA are accessible and transcriptionally active.

It is also important to note that the same modification of any of the 8 histone proteins in any nucleosome (the fundamental unit of chromatin) may not produce the same result.

For example: The methylation of H2 histone in the first nucleosome of a chromatin "string" may cause silencing while the methylation of H2 histone further down the chromatin "string" may cause activation.

It's alot of information but maybe one day you will be the one who solves the pattern! It sure is fascinating.