Genetic Disorders Health Article

Multifactorial genetic disorders

Statistics and studies of twins are often used to determine the genetic basis for multi-factorial genetic disorders (MFGDs). Because environment can play an important role in the development of these diseases, identical and fraternal twins who have been raised in different and identical homes are evaluated for these MFGDs. If fraternal twins have a higher than normal incidence and identical twins show an even higher rate of the disease, then genetic inheritance is believed to contribute to causing the disease. These disorders include some disorders associated with diet and metabolism, such as obesity, diabetes, alcoholism, rickets, and high blood pressure. Also included is the tendency to contract certain infections such as measles, scarlet fever, and tuberculosis. In addition, schizophrenia and some other psychological illnesses are strong MFGD candidates. Congenital hip, club foot, and cleft lip are also MFGDs. Various cancers are also correlated with genetic vulnerability.

Certain breast, colon, skin, and small-cell lung cancers have a genetic link. Familial breast cancer usually affects younger women, whereas some other types of breast cancer do not appear until later in life. Although familial breast cancer shows a very high degree of genetic dominance, it does not target every female relative and is thought to have another environmental or other unknown factor contribution. Familial colon cancer is attributed to polyposis—colon polyps that become cancerous. Some malignant melanomas of the skin are also highly heritable.

The tendency of some people to be more susceptible to a particular MFGD and not another is characteristic of human genetics. Although all healthy humans have a similar body form with very similar physiological functions, there is a tremendous diversity among humans that results from a diverse gene pool, which explains why certain groups of people with some genotypes in common would be more prone to a particular disease, while others would have resistance to the same disease. This diversity buffers the human race from being annihilated by a single agent.