| Single-gene (also called Mendelian or monogenic) - This | | | | disorder are Hypophosphatemia, Aicardi Syndrome, |
| type is caused by changes or mutations that occur in | | | | and Chokenflok Syndrome. |
| the DNA sequence of one gene. Genes code for | | | | Multifactorial inheritance -- Also called complex or |
| proteins, the molecules that carry out most of the | | | | polygenic inheritance. This type of inheritance is caused |
| work, perform most life functions, and even make up | | | | by a combination of environmental factors and |
| the majority of cellular structures. When a gene is | | | | mutations in multiple genes. For example, different |
| mutated so that its protein product can no longer carry | | | | genes that influence breast cancer susceptibility have |
| out its normal function, a disorder can result. There are | | | | been found on chromosomes 6, 11, 13, 14, 15, 17, and 22. |
| more than 6,000 known single-gene disorders, which | | | | Some common chronic diseases are multifactorial |
| occur in about 1 out of every 200 births. Some | | | | disorders. |
| examples are cystic fibrosis, sickle cell anemia, Marfan | | | | Examples of multifactorial inheritance include heart |
| syndrome, Huntington’s disease, and hereditary | | | | disease, high blood pressure, Alzheimer's disease, |
| hemochromatosis. | | | | arthritis, diabetes, cancer, and obesity. Multifactorial |
| Most of the genetic disorders featured on this web | | | | inheritance also is associated with heritable traits such |
| site are the direct result of a mutation in one gene. | | | | as fingerprint patterns, height, eye color, and skin color. |
| However, one of the most difficult problems ahead is | | | | Collaboration, education, and training - In addition to |
| to find out how genes contribute to diseases that have | | | | making important discoveries and developing new |
| a complex pattern of inheritance, such as in the cases | | | | therapies, the Center for Jewish Genetic Diseases has |
| of diabetes, asthma, cancer and mental illness. In all | | | | published numerous scientific articles, presented papers |
| these cases, no one gene has the yes/no power to | | | | at national meetings, and sponsored international |
| say whether a person has a disease or not. | | | | meetings so that scientists can interact and more |
| X-linked dominant disorders are caused by mutations | | | | rapidly advance the progress in these diseases. |
| in genes on the X chromosome. Only a few disorders | | | | We have also established productive collaborations |
| have this inheritance pattern. Males are more | | | | with researchers at the Hadassah Hospital - Hebrew |
| frequently affected than females, and the chance of | | | | University Medical School in Jerusalem as well as with |
| passing on an X-linked dominant disorder differs | | | | other scientists in Japan and Europe. |
| between men and women. The sons of a man with | | | | Most of these conditions involve mutations that lead to |
| an X-linked dominant disorder will not be affected, and | | | | the production of a nonfunctional enzyme, or one that |
| his daughters will all inherit the condition. | | | | is totally absent. In heterozygotes, the single good copy |
| A woman with an X-linked dominant disorder has a | | | | of the gene is generally able to produce sufficient |
| 50% chance of having an affected daughter or son | | | | enzyme to handle the normal workload. However, in a |
| with each pregnancy. Some X-linked dominant | | | | few cases, carriers as well as affected individuals |
| conditions, such as Aicardi Syndrome, are fatal to | | | | have to be careful about their diet, or may exhibit less |
| boys, therefore only girls have them (and boys with | | | | severe phenotypic effects. |
| Klinefelter Syndrome). Other examples of this type of | | | | |