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10.4 Metabolic, Triplet-Repeat & Mitochondrial Disorders — Test 2
Q1. Phenylketonuria (PKU) is inherited as a(n):✓ Autosomal recessive disorder
Q2. The enzyme deficient in phenylketonuria is:✓ Phenylalanine hydroxylase
Q3. A disease in which the urine turns black on exposure to air is:✓ Alkaptonuria
Q4. Albinism (oculocutaneous type 1) is caused by deficiency of the enzyme:✓ Tyrosinase
Q5. Galactosemia (classic form) results from the inability to metabolise galactose and is inherited as:✓ Autosomal recessive (homozygous affected)
Q6. Fragile-X syndrome (Escalante's syndrome) is caused by expansion of which trinucleotide repeat?✓ CGG
Q7. Which condition is frequently associated with males who have fragile-X syndrome?✓ Autism / intellectual disability
Q8. Which of the following is NOT a trinucleotide-repeat (triplet-repeat) disorder?✓ Duchenne muscular dystrophy
Q9. Myotonic dystrophy shows increasing severity and earlier onset in successive generations, a phenomenon called:✓ Anticipation
Q10. Most inborn errors of metabolism are caused by mutations in genes that code for:✓ Enzymes
Q11. In metabolic disorders, heterozygous carriers are usually clinically normal because:✓ They produce enough functional enzyme from the one normal allele
Q12. Mucopolysaccharidoses are genetic metabolic diseases that involve defects in:✓ Degradation (breakdown) of glycosaminoglycans
Q13. A characteristic feature of mitochondrial (mtDNA) disorders is:✓ A threshold effect, where symptoms appear once mutant mtDNA exceeds a critical level
Q14. Mitochondrial diseases such as MERRF and LHON are inherited:✓ Maternally (from the mother)
Q15. MERRF syndrome (myoclonic epilepsy with ragged-red fibres) is an example of a disease showing:✓ Heteroplasmy (mixed mtDNA populations)
Q16. Prader-Willi syndrome is most commonly caused by:✓ A microdeletion on the paternal chromosome 15
Q17. Cystic fibrosis is characterised by:✓ Abnormal chloride transport across epithelia
Q18. Hutchinson-Gilford progeria syndrome (premature ageing) is most often caused by a:✓ Point mutation in the LMNA (lamin A) gene
Q19. A galactosemic woman has a phenotypically normal daughter. The daughter marries a man whose sibling is galactosemic (parents are carriers). The chance their child is galactosemic, given the daughter is an obligate carrier and the man has a 2/3 chance of being a carrier, is:✓ 1/6 (≈ 2/3 × 1/4)
Q20. Match each disorder with its key feature and select the correct option.✓ A-ii, B-i, C-iv, D-iii