ABGC Board Exam (Genetic Counseling) Questions and Answers 100% Pass

ABGC Board Exam (Genetic Counseling) Questions and Answers 100% Pass Osteogenesis imperfecta - ANSWER -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 - ANSWER -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 - ANSWER -one gene causes more than one disease. many examples, but APOe is one -- hypercholesterolemia and Alz D Large deletions in mtDNA - ANSWER -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 2 | P a g e Created by Grace Amelia © 2025, All Rights Reserved. Leber hereditary optic neuropathy (LHON) - ANSWER -rapid onset of blindness as young adult, Gender bias: males > females maternal inheritance of mtDNA (mitochondrial genome) Complex I of ETC NARP - ANSWER -mtDNA (ATPase subunit 6 gene) neuropathy, ataxia, RP, DD/ID, lactic acidemia Leigh syndrome - ANSWER -early onset neurodegeneration w/hypotonia, DD, optic atrophy and respiratory abnormalities Inheritance: mtDNA (ATPase) or nuclear DNA genes MELAS - ANSWER -Inheritance: mtDNA (tRNA subunit) myopathy, mito encephalomyopathy, lactic acidosis, stroke-like episodes, may be mild (diabetes and deafness only) MERRF - ANSWER -mtDNA inheritance (tRNA) myoclonic epilepsy, ragged red fibers on histology, myopathy, ataxia, sensorineural deafness, dementia RMRP gene - ANSWER -RNA gene in nuclear genome (most are coded by mt genome) cartilage hair hypoplasia no protein product POLG - ANSWER -DNA polymerase gamma gene nuclear gene causes abnormal mitochondrial formation: deletions in mtDNA 3 | P a g e Created by Grace Amelia © 2025, All Rights Reserved. phenotype varies, but PEO is common Huntington disease - ANSWER -AD, CAG expansion, AD, paternal anticipation, in coding region (5' end) 36-39 CAG repeats - intermediate >40 repeats -- affected CAG repeat size correlates with severity of phenotype (more repeats, earlier onset) does not expand from normal range to disease-causing Fragile X - ANSWER -XL, CGG repeat in 5' UTR of FMR1 gene, maternal anticipation1/4000 male births, 2nd most common heritable form of ID (Down syn is #1). Always considered in differential diagnosis of a child (male or female) <45: normal 45-54: intermediate 55-200: premutation (FXTAS: ataxia/tremor syndrome and POI) >200: fragile X syndrome (females have 50-60% penetrance)