Typical/Atypical Mendelian Inheritance Flashcards
What is the pedigree pattern of AD disorders?
Vertical
What causes variable expressivity of AD disorders?
Modifier genetic variants (e.g. FGFR2 variants in BRCA2 mutations)
What is incomplete penetrance?
Absence of condition despite being inherited autosomal dominantly
What are some AD conditions?
Achondroplasia
Familial breast/colon cancer
AD polycystic kidney disease
NF1
What is the pedigree pattern of AR conditions?
Horizontal
What is consanguinity?
When mum and dad are related by blood - important to consider in AR conditions
How do AD and AR conditions distribute across males and females?
EQUAL frequency and severity
Can X-linked conditions show male-male transmission?
No - males will only ever receive Y chromosome from their father
In x-linked recessive what is “knights move”?
No male-male transmission but mostly/only males affected
Are females affected by x-linked recessive conditions?
Unlikely, but if affected then more mildly
What can cause “manifesting carriers” in females?
Scewed x-inactivation
What is an example of an x-linked recessive condition?
Duchenne muscular dystrophy
What is the sex ratio in x-linked recessive?
M»_space; F
What is the pedigree pattern of x-linked dominant?
Vertical
What is the sex ratio in x-linked dominant?
2 female : 1 male
What are examples of x-linked dominant conditions?
Vit D resistant rickets
male lethality =
Incontinentia pigmenti
Rett syndrome
What is genetic anticipation?
Increasing severity and decreasing age of onset in successive generations
Which conditions show genetic anticipation?
Huntington’s disease
Fragile X syndrome
Myotonic dystrophy
What is gonadal mosaicism?
Mutation might be in more than one egg or sperm cell in parent’s gonads
What is pseudo-dominant inheritance?
High carrier frequency or consanguinity makes a true AR condition appear AD (e.g. Gilbert syndrome)
Which parent can pass on mitochondrial DNA mutations?
Mother
