text: user12425: Transcription factors regulate the genes in different cells. That is, different cells have different sequence of genes that are transcribed (set on or off) by the RNA polymerase. This will help different types of cells to perform their own unique operation.
  So, why do the cells have to look different physically, if the their function is determined by the on/off sequence?
  NOTE: I am a neophyte in Bioinformatics. Any help on my building my conceptual knowledge is appreciated.
  
  user11884: There are many more contributors to the cell differentiation that the regulators. But one that you will encounter at an higher level is the chromatin status: if it is in the open status it allows transcripts to be on and being regulated (with all the further levels of regulations such as methylation, glycosylation etc). If the chromatin is off (the state is very condensed) very few transcript can be made from that region.
  Check this wikipedia page here
  
original_text: 12425: <p>Transcription factors regulate the genes in different cells. That is, different cells have different sequence of genes that are transcribed (set on or off) by the RNA polymerase. This will help different types of cells to perform their own unique operation.</p>
  <p>So, why do the cells have to look different physically, if the their function is determined by the on/off sequence?</p>
  <p><strong>NOTE:</strong> I am a neophyte in Bioinformatics. Any help on my building my conceptual knowledge is appreciated.</p>
   11884: <p>There are many more contributors to the cell differentiation that the regulators. But one that you will encounter at an higher level is the chromatin status: if it is in the open status it allows transcripts to be on and being regulated (with all the further levels of regulations such as methylation, glycosylation etc). If the chromatin is off (the state is very condensed) very few transcript can be made from that region.
  Check this wikipedia page <a href="https://en.wikipedia.org/wiki/Heterochromatin" rel="nofollow noreferrer">here</a></p>
  