Trait:A trait is any characteristic determined by genetics. Technically, genetic traits can be analyzed through segregation rather than quantitatively. A lethal trait is one that, when present in the genome, prevents the individual from having offspring. These traits must be new mutations because they are not inherited (since a potential parent with the trait would die before passing it on). A Mendelian trait follows the genetic laws established by Gregor Mendel. An example is the sickle cell trait, where an individual has one copy of the sickle cell gene but does not develop sickle cell disease, which requires two copies. If two people with the sickle cell trait have children, each child has a 25% chance of inheriting sickle cell disease. A nonpenetrant trait is a genetic trait present in the genome that does not express itself in the individual. In contrast, a penetrant trait is one that is expressed. For instance, if 100 people possess a particular genetic trait but only 80 express it, the trait's penetrance is 80%.
