What is used to trace a men’s genetics? why can this be used?

The researchers tracked genetic variation on the Y chromosome, the sex chromosome passed from father to son that encodes maleness, using a technique now widely used that was developed in the early 1990s by Underhill and colleagues in the lab of Luigi Cavalli-Sforza, professor emeritus of genetics. The method has given scientists a powerful window into ancient human migrations and prehistoric cultural shifts. The technique has also been adopted by some commercial genealogy services that offer Y-chromosome testing to the public.

This method was used because Y chromosome is only present in males.

Hope this helps have a good day

Smooth muscle is composed of involuntary muscles found within the walls of  organs and structures such as the stomach, esophagus, intestines, and blood vessels.  Smooth muscle can never be under your control since they are involuntary. Cardiac  muscle is also an involuntary muscle, found only in the heart.