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Mendelian Genetics


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What are the chances an unaffected person can pass on an AD trait to child?
How can you explain an AD disorder in a person with unaffected parents?
new mutation
Describe two AD disorders that can be caused by new mutations
Achondroplasia and Thanatophoric Dysplasia
Describe the penetrance of Achondroplasia
completely penetrant
Explain different heights that result from achondroplasia
variable expression
What gene is mutated for people with achondroplasia
FGFR3 fibroblast growth factor receptor 3
Describe thanotophoric dysplasia
lethal skeletal disease, death from respiratory insufficiency
How does a lethal gene stay in the gene pool?
constant rate of mutation 1 in 100,000 for thanatrophoric dysplasia
penetrance define
on or off
veriable presentation, like a dimmer switch on a light
holoprosencephaly is an example of what type of mutation
SHH mutation with variable expressivity
HPE is what type of mutation? AD or AR or mixed?
Thanotophoric Dyspliasia is AD AR or mixed
Achondroplasia is AD AR or other?
An example of sex limited expression
Time limited expression examples
HD and breast cancer
ex of germline mosaicism
campomelic dysplasia, aka brittle bone disease
what happens when s0x9 mutated
campomelic dysplasia
What is pseudo dominant inheritance?
It looks like dominant inheritance but is known to be AR. ex sickle cell and DFMB1
some contributing factors that cause Pseudodominant inheritance?
Consanguinity --> high rate of carriers
Can a person with a pseudo dominant mutation have children?
Yes. It is compatible with repro
What type of inheritance is Lowe Syndrome? AKA?
X linked oculo cerebro renal
Why might females show penetrance in X linked mutations?
Unfavorable Lyonization, two mutant Xs, 46 XY female, 45 X turner syndrome
what is an example of an xlinked letal disease
incontinentia pigmenti
In an x linked lethal disease, what is the ratio of male to female offspring?
2 females : 1 male All affected males die female moms have a smattering of miscarriages
In an x-linked lethal disease what is the chance that the mom is the carrier?
2/3rd. 1/3 chance it is a new mutation
Explain psuedoautosomal part of XY chromosomes and give example of disorder
Leri Weill The part of the Y and X chromosomes that display autosomal inheritance patterns, ex: SHOX gene
Define Digenic Inheritance
when there are mutant genes that normally cause a recessive trait but now one mutant copy of both genes together is enough to cause the trait
Describe the digenic pedigree characteristics
Vertical Transmission (gender doesn't necessarily matter) and recessive in that it has a 1 in 4 recurrance
under mendelian inheritance, mom and dad alleles are equally important and functionally equivalent, true or false?
true, that is the assumption we use in mendelian inheritance

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