Inheritance and testing in genetic disease Flashcards
Autosomal dominant inheritance
50% risk in offspring Transmission by M and F M and F equally affected Affected individuals have affected parent Every generation
Example of autosomal dominant disease
Huntington’s disease
1/10,000
Onset at 35-55, movement, cognitive and psychiatric problems
Autosomal recessive inheritance
25% risk in offspring
Parents are carriers
m and f equally affect
Usually no previous family history
Example of autosomal recessive inheritance
Cystic fibrosis
Mutation of CFTR
Main defects in lungs and pancreas due to mucus
X-linked recessive inheritance
No male-to-male transmission
M affected most
Transmitted through female carriers
Example of x-linked recessive
Haemophilia A and B
Duchenne muscular dystrophy
X-linked dominant inheritance
M and F affected by F more common
Affected can transmit to daughters but not sons
X-linked dominant inheritance with male lethality
Male is severely affected
Survival is unusual
Often males have addition X chromosome
X-linked dominant inheritance with male sparing
Only females affected
Mechanism unclear
Example of x-linked dominant disease
Rett syndrome
Y-linked inheritance
Affected males transmit to all sons
Males only
Mitochondrial inheritance
Can appear in every generation
Affects M and F
Fathers don’t pass to children
Examples of mitochondrial inheritance disease
Leber’s hereditary optic neuropathy
Leigh syndrome
What are genetic pedigrees?
Graphical representation of family tree
Diagnostic testing
- To confirm or rule out a specific genetic/chromosomal condition which is suspected
- Floppy babies tested for PWS, SMA and MD
- Children with learning disability tested for fragile X syndrome and have aCGH analysis
- Familial cancer syndromes, cystic fibrosis, Huntingdon’s
- Can be performed at any point in life
- Woman over 35 trying to get pregnant indicates genetic condition
