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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
Created by Grace Amelia © 2025, All Rights Reserved.
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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
Created by Grace Amelia © 2025, All Rights Reserved.
