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.
Single genes code for most traits. Multiple genes, not just a single gene, determine most traits in humans such as height, eye color, and skin color. When a trait is controlled by more than one gene it is called polygenic.