Autosomal Dominant Conditions Flashcards
What is the inheritance pattern of AD?
All offspring have 50% chance of inheriting mutation.
Can male - male transmission occur in AD?
Yes!
Only in AD does male to male transmisison occur!
why is hereditary haemochromatosis an exception to the rule?
‘hereditary’ usually prefixs AD.
Hereditary Haemochromatosis is in fact AR, but carrier frequency is high (pseudo dominant)
What is meant by / what is inheritance pattern of pseudo dominance?
if the partner of an affected person is a carrier: 50% of their offspring will be affected.
- Penetrance is higher in males.
Most metabloic disorders are AR, what are the exceptions?
- Hunter’s
- G6PDD (favism)
- Childhood adrenalleukodystrophy
* All XLR - Familial hypercholesterol
- Acute intermittent porphyria
* All AD
What is the inheritance pattern of AR conditions?
Mutations to both alleles of autosomal gene.
If both parents affected:
- child has 1/4 chance of affected
- child has 2/4 chance of carrier
Which are the commonest AR condition?
CF
Haemochromatosis
XLR conditions have which inheritance pattern?
Mutation of gene on X chromosome.
Affects males
No male-male transmission.
How are the XLR genes passed down?
All daughters of affected male = women carriers.
Sons of women carrier = 50% affected
Daughters of women carrier = 50% of being carrier.
Which are the commonest XLR conditions?
Fragile X
Muscular dystrophies
Red/green colour
XLD conditions have which inheritance pattern?
Mutation to one copy of gene on X but both male and females mutation carriers are affected
How are XLD genes passed down?
No male to male.
All daughters of affected male are affected.
All offspring of affected female have 50% chance of affected.
Examples of XLD conditions:
- Vitamin D resistant rickets
- Rett syndrome (girls, progresssive microcephaly, hand movements)
- Periventricular nodular heteropia (asc. with epilepsy + LD)
