Steven has the dominant tongue rolling phenotype but he does not know his genotype. his wife has the recessive non-tongue rolling trait. if their son cannot roll his tongue this means

Steven has heterozygous genotype.

Explanation:

Tongue rolling is a dominant trait, that means the trait can express itself at the homozygous dominant and as well as in the heterozygous condition. The recessive homozygous condition is not able to express this trait.

Steven can roll his trait, this means his genotype is either homozygous dominant or heterozygous. The wife is recessive for the trait. Their son cannot roll his tongue, this means the Steven is heterozygous dominant. If the Steven is homozygous dominant his son will be able to express the trait.

Thus, the answer is Steven has heterozygous genotype.

Systemic circuit is defined as one of the two circuit of circulation that occurs in human body.

The circulatory system is divided into two phases in the human body. They are:

A. Pulmonary circulation

B. Systemic circulation.

The pulmonary circulation is the short circuit of circulation that starts from the right ventricle, goes to lungs via pulmonary artery and returns to left auricle via pulmonary vein.

The systemic circulation is the bigger circuit that starts from the left ventricle, goes to each and every organ of the body via aorta, and returns to the right auricle via venacava.