Table 1 Complex versus single-gene disorders
FEATURES | COMPLEX | SINGLE GENE |
|---|---|---|
Gene | Segregates | Segregates |
Disorder | Clusters | Segregates |
Number of genes/gene products | Multiple | Primarily one (although disease modifier genes may be involved) |
Role of environmental or occupational exposures | Important | Often overridden by effect(s) of gene mutation |
Age of onset | Often older | Often younger |
Risk for relatives of probands | Less predictable, often small | More predictable, often large |
Healthcare burden | High | Relatively low |
Prevalence | Common | Relatively rare |
Variability in expression/phenotype | Generally more variable | Generally less variable |