What do you already know about the difference between dominant and recessive traits? Or sex-linked and autosomal traits? Dominant traits are the traits that are normally shown in an organism. Recessive traits are the traits that are not normally shown in an organism overpowered by the dominate trait.
In mammals, the powerful muscle that aids in breathing is the diaphragm. This muscle expands and contracts the chest cavity and forces air in and out of the lungs. Hope that helped =)
