Practice questions › Davidson's Principles of Medicine › Davidson's Medicine - Part 3: Clinical Medicine
Davidson's Medicine - Part 3: Clinical Medicine, Part 3 - Clinical Medicine (overview) MCQs
Davidson's Medicine - Part 3: Clinical Medicine · Davidson's Principles of Medicine · 29 practice questions
- Matching conditions to inheritance patterns
- Autosomal dominant conditions - gene identification
- Alpha-1-antitrypsin deficiency - genetic variants
- Autosomal dominant vs recessive pedigree features
- Mitochondrial energy metabolism
- Alpha-1-antitrypsin deficiency clinical features
- Autosomal recessive inheritance - Alpha-1-antitrypsin deficiency
- Mitochondria structure and origin
1. A genetic counsellor is explaining inheritance patterns in a family with Duchenne muscular dystrophy. Edward's maternal uncle died of the disease, but Edward's mother is unaffected. If Edward's healthy sister is confirmed to be a carrier and later has children with an unaffected man, what proportion of her sons would be expected to be affected?
- A50%
- B100%
- C25%
- D75%
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A. 50% Female carriers of X-linked recessive conditions pass the mutant allele to half of their offspring on average; since only male offspring can be affected (having only one X chromosome), 50% of her sons would be expected to be affected.
2. A biochemist is studying how fatty acids and glucose both contribute to acetyl-CoA production despite requiring different mitochondrial entry mechanisms. Which statement correctly distinguishes how these two substrates gain access to the mitochondrion for energy metabolism?
- AGlucose enters mitochondria directly, while fatty acids require conjugation with carnitine before transport
- BBoth glucose and fatty acids enter mitochondria directly without any prior modification
- CGlucose must first be converted to pyruvate via glycolysis before mitochondrial import, while fatty acids require conjugation with carnitine for transport
- DFatty acids are converted to pyruvate before entering mitochondria, while glucose is transported directly using carnitine
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C. Glucose must first be converted to pyruvate via glycolysis before mitochondrial import, while fatty acids require conjugation with carnitine for transport The text explains that glucose is first metabolised to pyruvate via glycolysis before being imported into mitochondria, whereas fatty acids are transported into mitochondria after conjugation with carnitine, then undergo beta-oxidation.
3. A clinician reviews a large pedigree with an autosomal dominant cancer susceptibility syndrome. Some family members who carry the pathogenic variant never develop cancer, while others who do develop cancer show widely differing ages of onset and tumour types. Which pair of concepts best explains these two distinct observations?
- ABoth observations are explained by incomplete penetrance alone
- BPenetrance explains why some carriers never develop cancer; expressivity explains the varying severity and presentation among those affected
- CPenetrance explains the varying tumour types and onset ages; expressivity explains why some carriers never develop cancer
- DBoth observations are explained by variable expressivity alone
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B. Penetrance explains why some carriers never develop cancer; expressivity explains the varying severity and presentation among those affected Penetrance is the proportion of variant carriers who develop the disease phenotype at all, while expressivity describes the level of severity of each aspect of the phenotype in those who are affected.
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