2. Learning Objectives

2.2. Gene regulation makes cells different

The different patterns of gene expression cause our various cell types to have different sets of proteins, making each cell type uniquely specialized to do its job.  For example, the liver functions to remove toxic substances like alcohol from the bloodstream. By expressing genes encoding the enzyme called alcohol dehydrogenase. This breaks alcohol down into a non-toxic molecule.
Likewise the neurons in brain do not  function to remove toxins from the body, so they keep these genes unexpressed, or “turned off.” Similarly, the cells of the liver do not send signals using neurotransmitters, so they keep neurotransmitter genes turned off.
It is interesting to know that humans and chimpanzees are about 98.8%identical at the DNA level. But the protein-coding sequences of some genes are different between humans and chimpanzees.  This  contributes to the differences between the species explaining the importance of gene regulation and differential expression of the genes.