Question

All the cells in our bodies have the same genome, yet they are differentiated based on gene expression. In eukaryotes, gene expression can be controlled at several different levels. Discuss ONE type of control that occurs at the chromosomal/DNA level and ONE that occurs at the mRNA level. Compare these two controls in terms of timing and coordination within the cell.

Answer 1

You might want to think about the actual states in which DNA exists in a cell. DNA is essentially a very long piece of string that, if not wound up very precisely, is very liable to get tangled. So it is packed and arranged into chromosomes in a very specific way. The cost of that being that when DNA is folded up in this precise structure, it cannot be transcribed into RNA because the transcriptional enzymes cannot reach the genes. So there is this balance between efficient mess control - how tightly and safely the DNA is packed - and whether or not the cell can still access genes in that DNA...