|
Exception |
Definition |
Example | |
|
Multiple Alleles
|
Many variants or degrees of a phenotype occur |
Cystic Fibrosis | |
|
Codominance
|
A heterozygote’s phenotype is distinct from and not intermediate between those of two homozygotes |
AB0 Blood types | |
|
Incomplete Dominance |
A heterozygote phenotype is intermediate between those of two homozygotes |
Familial Hypercholesterolemia
| |
|
Lethal Allele Combinations |
A phenotypic class does not survive to reproduce |
Spontaneous abortion | |
|
Pleiotropy
|
The phenotype includes many symptoms, with different subsets in different individuals |
Porphyria variegata | |
|
Phenocopy |
An environmentally caused condition has symptoms and recurrence pattern similar to those of a known inherited trait |
Infection | |
|
Heterogeneity |
Different genotypes are associated with the same phenotype |
Hearing impairment
| |
|
Epistasis |
One gene masks or otherwise effects an other’s phenotype |
Bombay phenotype | |
|
Penetrance |
Some individuals with a particular genotype do not have the associated phenotype |
Polydactyly | |
|
Expressivity |
A genotype is associated with a phenotype of varying intensity |
Polydactyly | |
