Other factors affecting expression
Anticipation
- A special type of variable expression
- Tendency of some dominant disorders to become more severe with successive generations
- Found to be caused by expansion of tri-nucleotide repeats
- Repeat length increases with each generation
- Severity of disease increases with increased repeat length
- Found in Fragile X syndrome, myotonic dystrophy and Huntingtonās disease
Imprinting
- Expression of an allele depends on which parent it was inherited from - allele is somehow Īmarkedā
- One particular case- a deletion of 15q12 results in 2 different syndromes depending on which parent it was inherited from (Prader-Willi syndrom from dad, Angelman syndrome from mom)
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