Roger is relieved that he does not have LQT7, which affects skeletal as well as cardiac muscle, causing short stature and scoliosis. He is also glad that he doesn't have LQT8, which causes many symptoms, or either of two types that also cause deafness. These other forms of the condition, with more than one symptom, exhibit: a. invariable expressivity. b. complete penefrance. c. genetic homogeneity. d. pleiotropy. e. phenocopy.

D) pleiotropy

Explanation:

Long QT syndrome is a type of syndrome which is characterized by having a long QT interval of the cardiac cycle.

Log QT syndrome occurs when the genes which control the formation of ion channels like sodium, potassium gets mutated as a result of which these channels are not formed or if formed are blocked. This slows down the ventricular repolarization as a result of which enough blood does not reach the organs.

The disease is genetical and is considered an autosomal recessive form. The gene for this is known as LQT and the associated genes are LQT7 and LQT8.

These associated genes produce additional symptoms along with long QT like short stature therefore these genes are considered pleiotropic where gene shows multiple effects.

Thus, Option-d is the correct answer.