Genetic Disorders and Biochemical Pathology — Flashcards

Flashcard 191: Segawa syndrome is due to the defective _____ enzyme required for BH4 synthesis

Answer: GTP cyclohydrolase I

Flashcard 192: Presenilin 1 & 2 code for components of the enzyme _____, which leads to production of Amyloid-beta (Aβ) and its deposition in Alzheimer's disease.

Answer: γ-secretase (Gamma-secretase)

Flashcard 193: What is the inheritance pattern of Brunner's syndrome?

Answer: X-linked recessive

Flashcard 194: The ratio of the phenylalanine (Phe) level 2 or 3 hours after a BH4 loading test to the urine _____ level has high sensitivity and specificity for diagnosing Segawa syndrome.

Answer: neopterin

Extra: In Segawa syndrome (GTP cyclohydrolase I deficiency), neopterin production is severely impaired. The ratio of post-load phenylalanine to urinary neopterin is an effective diagnostic marker because phenylalanine levels remain relatively stable (or slightly elevated) while neopterin levels are extremely low.

Flashcard 195: There is impaired synthesis, processing, or ligand binding of _____ in patients of Imerslund-Grasbeck syndrome

Answer: cubilin

Flashcard 196: The mutations contributing to Menieres disease are found in the short arm of chromosome _____.

Answer: 6

Flashcard 197: _____ levels of coproporphyrin in urine is seen in Rotor syndrome

Answer: Increased

Flashcard 198: _____ paradox states that risk of expressing mental retardation in fragile X syndrome increases in later generations

Answer: Sherman's

Flashcard 199: Which gene is mutated in congenital cataract?_____

Answer: Crystallin

Flashcard 200: MELAS is due to defects in mitochondrial proteins like ETC complex _____ or complex _____.

Answer: I; IV