Examples of Inheritance in Humans
| Table 1. Some major recessive genetic disorders caused by single gene mutations. | ||||
|---|---|---|---|---|
| Disease | Frequency | Symptoms | ||
| Cystic fibrosis | 1 in 2000 (N. Europeans) | Recurrent lung infections, pancreatic exocrine deficiency, male sterility | ||
| a1 - Antitrypsin deficiency | 1 in 5000 to 1 in 10,000 (N. Europeans) | Liver failure, emphysema | ||
| Phenylketonuria | 1 in 2000 to 1 in 5000 (N. Europeans) | Mental retardation | ||
| Tay-Sachs disease | 1 in 3000 (Ashkenazi Jews) | Neurological degeneration, blindness and paralysis | ||
| Sickle cell anemia | 1-2 in 100 (Africa where malaria is endemic) | Anaemia | ||
| Hemochromotosis | 1 in 500 | Excessive iron accumulation in adults, resulting in diabetes, liver cirrhosis and heart failure | ||
| Thalassemias | 1-2 in 100 (Mediterranean and Asia where malaria is endemic) | Anaemia | ||
| Table 2. Some major dominant genetic disorders caused by single gene mutations. | ||||||
|---|---|---|---|---|---|---|
| Disease | Frequency | Symptoms | ||||
| Familial hypercholesterolaemia | 1 in 500 | Premature heart disease | ||||
Familial breast cancer
|
|
1 in 800 (USA) 1 in 100 (Ashkenazi Jews 1) | High lifetime risk of breast and ovarian cancer. Earlier onset than sporadic cases. | |||
| Familial Alzheimer's disease | 10 % lifetime risk at age 80 2 | Dementia. Earlier onset than sporadic cases. | ||||
| Hereditary non-polyposis colorectal cancer | 1 in 400 3 | Colon cancer not associated with polyps | ||||
| Familial adenomatous polyposis | 1 in 8000 | Bowel polyps that may become malignant | ||||
| Neurofibromatosis | 1 in 4000 | Tumors of peripheral nerves. Cafe-au-lait pigment spots on skin | ||||
| Huntington's disease | 1-2 in 10,000 | Involuntary choreiform movements. Dementia. | ||||
| Myotonic dystrophy | 1 in 8500 | Myotonia, heart defects, and cataracts. | ||||
| Familial retinoblastoma | 1 in 14,000 | Multiple unilateral and bilateral tumors of the retina | ||||
| 1 | BRCA1 and BRCA2 each have a frequency of 1 in 100 in Ashekanazi Jews. | |
|---|---|---|
| 2 | Alzheimer's disease is normally a complex disease with genetic and environmental components. A subset of cases show early onset and simple autosomal dominant inheritance. The proportion of total cases represented in this category is unknown. | |
| 3 | Wide range of estimates from 1 in 200 to 1 in 10,000. |