Week 4 Day 4 Flashcards
(12 cards)
How are mitochondrial disorder inheritance seen in pedigree?
Maternal inheritance exclusively.
How do mitochondrial disorders usually manifest?
As nueromuscular disorders.
Why can mitochondrial disorders show incomplete penetrance?
Only a subset of mitochondria are inherited and it is possible to only inherit healthy mitochondria.
Review imprinting.
It’s difficult to tell this type of inheritance so you have to somewhat rely on the clinical manifestation.
How does uniparental disomy lead to unexpected diseases?
If the child were to receive 2 copies of a defective gene from the parent, they would express a normally autosomal recessive disorder.
This is also possible in the case of imprinted genes.
How are autosomal dominant disorders that confer completely reduced reproductive fitness possible?
New mutations.
How can an autosomal dominant disorder be seen in multiple affected children of unaffected parents.
Germline mosaicism.
How can embryonic lethal disorders be seen in adults?
A new mutation on a subset of embryonic cells, causing adult cell mosaism.
Describe why children who inherit a disorder, may express the disorder at younger age?
Anticipation.
DNA repeat gets longer and longer over time which causes the disorder sooner. (probably from aggregation)
- The triplet repeating causing Huntington disease is
A. Located in the promoter B. Within the 5’-UTR C. Found in an exon D. Within an intron E. Within the 3’-UTR
C. Huntington disease is caused by expansion of a CAG repeat contained in an exon and encoding polyglutamine tracts. The pathological protein aggregates within neurons, where it is toxic.
- The triplet repeat causing Huntington disease
A. Exerts its effect as the transcriptional level by become hypermethylated and inhibiting transcription
B. Exerts its effect primarily at the post-transcriptional, pre-translational level by decreasing mRNA stability, export, and/or translation
C. Exerts its effect primarily at the post-transcriptional, pre-translational level by inhibiting splicing through interrupting an exon/intron splice boundary
D. Exerts its effect at the post-translational level, by becoming translated into a polyglutamine tract, thus changing the protein sequence, structure, and/or function
E. B and C
D, as explained previously.
- Who is at greater risk for having a son with the fragile X syndrome (assuming that both woman are currently pregnant): a an affected woman with the fragile X full mutation or an unaffected woman with the fragile X full mutation?
A. The affected woman
B. The unaffected woman
C. Both equally
D. Neither, recalling that for obscure reasons the eggs of women with the full mutation only contain premutation length mutations
C. Penetrance in fragile X is a function of the degree of skewing in Lyonization for this X-linked gene and has no relationship to the probability of its transmission from within the germline. It is therefore only of significance that either woman has the full mutation.
