Within a pedigree, only males exhibit a trait of interest and the trait commonly passes from a male to his grandsons through his daughters and never through his sons. What is the most likely mode of inheritance, assuming complete penetrance?

X-linked/Sex-linked recessive inheritance

Explanation:

The most likely mode of inheritance of the trait is an X-linked recessive inheritance.

The sex chromosome of a male is XY while that of a female is XX. The Y chromosome is hypothesized not to carry any allele ordinarily. Hence, a male child only needs to inherit one affected allele to become affected for recessive X-linked traits.

During gamete formation, the sex chromosome of the male segregates into X and Y gametes while that of the female segregates into X and X gametes. During fertilization, the X gamete of the male is usually inherited by the female while one of the X gametes of the female is usually inherited by the male.

Assuming a father is affected for an X-linked recessive trait, the affected X chromosome will be passed to a female child and such a child would be a carrier, rather than being affected since she requires the two X chromosomes to be affected in order to exhibit the trait.

The affected X chromosome is thus passed to her male child according to the law of inheritance of the sex chromosome. Hence, the grandson of the affected man inherits the trait through the daughter of the affected man.

Explanation:

Muscle tissue is one of four types of tissues found in animals. There are three different types of muscles in the body

The skeletal muscle is made up of voluntary muscles, usually attached to the skeleton. Skeletal muscles move the body. They can also be involuntarily contracted by reflex. For example, you can choose to move your arm, but your arm will move automatically if your fingers were burned in a kitchen burner. This voluntary contraction begins with a thought process. A signal from your brain tells your muscles to contract or relax. Quickly, contract and relax the muscles in your fingers a couple of times. Think about how fast these signals must travel through your body for this to happen.

The smooth muscle is made up of involuntary muscles that are found in the walls of organs and structures such as the stomach, stomach, intestines and blood vessels. These muscles push materials such as food or blood through the organs. Unlike skeletal muscles, smooth muscle can never be under conscious control.

The heart muscle is also an involuntary muscle that is found only in the heart. Cardiac muscle fibers contract all joints, which generates enough force to pump blood throughout the body.