Why do genetic mutations often impact more than one system in the body?

Genetic mutations often affect more than one organ system because most organ systems are not completely independent of each other. They work collaboratively together to ensure that the entire organism functions properly.

For example, a simple overview of the circulatory system will say that it is made of the heart, the blood, and the blood vessels. The right side of the heart is in charge of pulmonary circulation. Blood is being sent to the lungs,...

Genetic mutations often affect more than one organ system because most organ systems are not completely independent of each other. They work collaboratively together to ensure that the entire organism functions properly.

For example, a simple overview of the circulatory system will say that it is made of the heart, the blood, and the blood vessels. The right side of the heart is in charge of pulmonary circulation. Blood is being sent to the lungs, and the lungs are part of the respiratory system. If the lungs weren't there, the blood would never be oxygenated. If the blood wasn't being sent there, the lungs would have nothing to exchange their gas loads with. 

More than likely, any kind of genetic mutation occurring within a particular system will absolutely affect another system because each system works in close relation to at least one other system. The change in one system could enhance both systems, or the change could hinder the other system.

Let's use the circulatory system and respiratory system relationship. Let's say that a particular mutation caused a person to double the number of alveoli within each lung. We'll have to assume that each additional alveoli is also wrapped up in the normal capillary bed in order to ensure gas exchange between it and the blood. More alveoli and increased lung size will allow for more oxygen to be inhaled and absorbed into the blood. The higher levels of oxygen in the blood means that a person's breathing rate can stay lower for longer periods of time (during exercise for example). The heart will also maintain a lower overall heart rate because the blood is carrying more oxygen per breath.