Drugs and other chemicals are examples of how environmental factors affect gene expression. These drugs can either 'activate' or 'inhibit' the expression of genes that you have. For example, taking drugs while being pregnant affects the genetic makeup of the baby inside you.
Snug but do not make it too tight because if it is very tight against the skin then blood circulation will decrease.
However, if the friend appears to be very injured, he/she might need to get examined by a professional
Lots of mitochondria would be present.
