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30. A 10 year old girl is diagnosed with Marfan Syndrome, an Autosomal dominant ocndition. An extensive revies of her pedigree indicates no previous family history of this disorder. Which of the following is the most likely explanation for this pattern?

A. Highly variable expression of the disease phenotype

B. Incomplete penetrance

C. Mitochondrial compensation in the mother

D. New mutation transmitted by one of the parents to the affected girl

E. Pleiotrophy


the answer is d


yes D is correct




Yes. D. anyone want to say why?


well marfan syndrome is autosomal dominent disease mean it need just one allele to express the disease . so multiple generation will be affected in autosomal dominent disease.

as there are no family history in this Q so its probably due to mutation in the parents DNA that is transferred to the kid

hope this will help


Right.... Why can we rule out B) Incomplete penetrance???


in incomplete penetrence we usually have a f/h of ppl with the disease, and a few obligate carriers who do not..we know they r obligate as lets say , all their children have the disease, one or more parents, grandparents, have the disease...

hence we can say for sure that the person duz HAVE the mutation but is NOT EXPRESSING IT. here the story is different altogether...


Yes, the penetrance of Marfans is high, and NO previous family history, so if she was the first one to get it, it must have been a new mutation.


new mutation


i also go with D, but incomplete penetrance is also a feature of autosomal dominant disorders.



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