The indoor cabinet also typically includes a furnace (or the inside part of a heat pump). The indoor and outdoor units are connected by a refrigerant line. Greater energy efficiency possibilities - Split air conditioning systems have SEER ratings from 13 to 23.
A single gene trait is controlled by a single gene. Polygenic traits are controlled by two or more than two genes on different chromosomes. These genes are described as polygenes. Examples of human polygenic inheritance are height, skin color and weight.
A recessive trait is a trait caused by a recessive gene, which means that someone must inherit two copies of the gene for the trait to manifest. By contrast, a dominant trait only requires one copy of the gene. The concept of dominant and recessive traits in genetics was put forward by Gregor Mendel, a 19th century scientist who is often regarded as the father of genetics, thanks to his extensive work in the field.