Explain howmuscle structure, a gene controlled trait, can be influenced by the environment

The simple answer is - imagine someone who is working out regularly and someone who isn't. 

The person who work out regularly may have more muscles than the other one, but at the same time, he has a worse genetic predisposition for muscle gain. The guy who does not work out on the other hand, has a better genetic predisposition for muscle gain, yet does not work out. 

This is how our environment can influence muscle structure. 

Ithink the correct answer would be that since the disease is passed by a hand shake and can be cured with antibiotics that it could be an infection. an example could be that once when i was working in a bush camp, i got blood poisoning from blood blisters that got infected. our cook did not wash his hands after going to the bathroom and he passed staphyloccus on to the crew he fed. one other person also got a bad similar infection on the side of his face. i had to be rescued by helicopter and taken to the hospital so i wouldn't die!