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Which of the following genetic principles best explains the findings in this family? A 40-year-old woman comes to the physician for genetic counseling because of a family history of muscle weakness. She says that she has not sought treatment because her symptoms are not severe, but her children have profound muscle weakness and fatigue. Sequence analysis of mitochondrial DNA shows a mutation in 50% of the mothers mitochondria DNA and in 100% of each other children's mitochondrial DNA. A pedigree is shown.





A. Anticipation
B. Genetic drift
C. Heteroplasmy
D. Imprinting
E. Pseudodominant inheritance

This question is part of NBME 13 section 1 (qst 1-50)
Asked by Wyatt Williams, Last updated: Sep 26, 2020

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3 Answers

C. Block

C. Block

Find happiness in writing new things.

C. Block
C. Block, English Professor, M.A, Ph.D, Buffalo

Answered May 30, 2019

This is heteroplasmy, which means that C is the answer to this question. This is the process wherein there is more than one type of organelle genome that is available within the cell. This can sometimes determine how severe certain mitochondrial diseases are.

Different tests are available to assess the presence of DNA heteroplasmy. Different approaches are possible, depending on what exactly the patient would need to find. Does the patient need to know if heteroplasmy is present or what type of proportion of the variant is available? These are things that the patient needs to discuss with the doctor to determine the proper test to take.

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Robert Hazlewood

Robert Hazlewood

Here to relax my mind a bit

Robert Hazlewood
Robert Hazlewood, Senior Executive, MBA, Louisville

Answered Apr 19, 2019

C is the answer to this question. If in case you are not familiar with what a heteroplasmy is, this is the condition wherein there is more than one type of organellar genome that is present. This may occur in a cell or an individual. You can check the severity of the different mitochondrial diseases based on this.

Take note that not all cells may become affected by this. There are instances when one cell may exhibit signs of heteroplasmy. Take note that mitochondrial DNA heteroplasmy can be inherited which means that the children of the 40-year-old-woman may have inherited a more severe version based on the pedigree.

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Wyatt Williams

Wyatt Williams

Wyatt Williams
Wyatt Williams

Answered Jul 13, 2018

Heteroplasmy
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