nbme 13 ,Q4 - mdkhayat

[ArchivalUser]

A 60 year old man comes to the physician because of 2 year history of progressive shortness of breath with exertion his two younger siblings have similar symptoms his mother died of dilated cardiomyopathy . physical examination shows jugular venous distention and ankle edema there is hepatomegaly. inspiratory crackles are heard over both bases. a chest x-ray shows cardiomegaly and pulmonary conjestion angiography confirms dilated cardiomyopathy. an artial endocardial biopsy specimen shows abnormal sarcomeres with paracrystalline inclusion in mitocondria. sequencing of mitochondrial DNA shows G-to-A transition. this results in an added A:T base pair to the 3' end of tRNA thus shortening the C loop which of the following is the most likely effect of this mutation on mitochondrial function?

A] decreased mRNA stability
B] decreased protein synthesis
C] decreased replication
D] increased mRNA stability
E] increased protein synthesis
F] increased replication

[ArchivalUser]

B

[ArchivalUser]

explain please

[ArchivalUser]

Your basically stopping tRNA from carrying amino acids
This prevents them from transferring to mitochondria for formation of protein synthesis...
It's been a while since I touched biochem but I recall mitochondria has its protein synthesis as well.
That's what's being asked here

[ArchivalUser]

zen786 ,tell me how it affects carrying of aas by tRNA?

[ArchivalUser]

If you recall Kaplan biochem and also uworld question and your first aid tRNA section.
tRNA carries amino acid
Aug
Gua
and etc and the c loop is the stop area. In this question it fell short hence less amino acid.
If you look at the first aid imagine in biochem Ull get the exact mechanism.