Autosomal Dominant Disorders Flashcards Preview

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Flashcards in Autosomal Dominant Disorders Deck (13):

Define Autosomal Dominant Disorders

Heterozygotes with one copy of altered gene have the condition


What is the pedigree analysis of ADD

In each generation
Males = Females
Affected people have affected children
Male to male transmission
Children of affected + unaffected are 1/2 risked


How does the gene cause its effects

Dominant/recessive refer to phenotype
Effect due to gene dosage ie. absence of protein
Most dominant give rise to truncated proteins


What does dominant/recessive pattern depend on

Depends on how cell responds to 1/2 amount of gene product
Dominant = 1/2 amount of structural protein
Recessive = 1/2 normal activity of enzyme


Why do family members that have same altered allele have different signs/symptoms (Variation in expression)

Interaction between other genes from unaffected parent


What is penetrance

Everyone with pathogenic gene alterations shows at least one clinical sign


What is non-penetrant

Has gene but no signs


What is incomplete penetrance

Not 100% of people with disease genotype will show signs


What is the clinical implications of penetrance and variation in expression

Can make person appear they dont have autosomal dominant condition but in actual fact they have the gene


What does new mutations mean

Increase with paternal age due to greater umber of germ cell divisions


What is anticipation

Age of onset decreases
Severity of phenotype increases
in Successive generations
Correlated with repeat length which increases as gene transmitted down


How can kids be affected from unaffected parents

Gonadal mosicism for new mutations
Occurs in mitosis after fertilisation
Up to 50% probability of inheritance


What do you know about Huntington's Disease

More than 34 repeats of CAG
Protein aggregates in brain cell and cause progressive cell death
Symptoms occur if cells accumulate past critical number