ABGC Board Exam 2024 (Genetic Counseling) A+ GRADED

Osteogenesis imperfecta correct answers Genes: COL1A1 (ch17; more severe pheno w/mutn b/c there are 2 alpha strands vs. 1 beta strand), COL1A2 (ch7), form protein triple helix Type I -- AD, mild, blue sclera, brittle bones, no deformity collagen: normal quality, AMOUNT is reduced Type II: AD, neonatal lethal, abnormal collagen Type III: AD, progressive deforming, fractures at birth, small, blue sclera Type IV: AD, normal sclera, mild/mod bone deformity, short stature, fractures Alzheimer disease correct answers Usually complex inheritance, FDR risk 38% over lifetime APOe4 allele confers risk, modifier of monogenic AD genes (causes earlier onset). APOe2 allele is protective for AD. AD genes: APP, PSEN1 (50% of AD cases), PSEN2 Pleiotropy correct answers one gene causes more than one disease. many examples, but APOe is one -- hypercholesterolemia and Alz D Large deletions in mtDNA correct answers Usually NOT maternally-inherited Pearson syndrome: pancreatic insufficiency, pancytopenia, lactic acidosis, KSS in second decade Kearns-Sayre syndrome: progressive myopathy, PEO, cardiomyopathy, heart block, ptosis, retinal pigmentation, ataxia, diabetes Leber hereditary optic neuropathy (LHON) correct answers rapid onset of blindness as young adult, Gender bias: males > females maternal inheritance of mtDNA (mitochondrial genome) Complex I of ETC NARP correct answers mtDNA (ATPase subunit 6 gene) neuropathy, ataxia, RP, DD/ID, lactic acidemia Leigh syndrome correct answers early onset neurodegeneration w/hypotonia, DD, optic atrophy and respiratory abnormalities Inheritance: mtDNA (ATPase) or nuclear DNA genes MELAS correct answers Inheritance: mtDNA (tRNA subunit) myopathy, mito encephalomyopathy, lactic acidosis, stroke-like episodes, may be mild (diabetes and deafness only) MERRF correct answers mtDNA inheritance (tRNA) myoclonic epilepsy, ragged red fibers on histology, myopathy, ataxia, sensorineural deafness, dementia RMRP gene correct answers RNA gene in nuclear genome (most are coded by mt genome)