Genetic Disorders Flashcards by Frances Catipay

Point mutation where altered DNA codes for the same AA

Silent mutation

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Point mutation where altered DNA codes for a diff AA

Missense mutation

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Frameshift mutation of dystrophin gene

Duchenne muscular dystrophy

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Nonframeshift mutation of dystrophin gene

Becker’s muscular dystrophy

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Insertion or deletion of one or more nucleotide shifts the reading frame of the DNA strand

Frameshift mutation

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Amplification of a sequence of 3 nucleotides; presents with anticipation

Trinucleotide-repeat mutations

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Type of mutation in Huntington’s disease, myotonic dystrophy, fragile X syndrome, Friedrich’s ataxia

Trinucleotide-repeat mutations

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X-linked recessive disorders

Be Wise Fool’s GOLD Heeds Silly Hope

Bruton's agammaglobulinemia
Wiskott-Aldrich syndrome
Fabry's disease
G6PD
Ocular albinism
Lech-Nyhan syndrome
Duchenne's muscular dystrophy
Hunter syndrome
Hemophilia

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Affected heterozygous female to half her sons and half her daughters

X-linked dominant

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Transmitted only through the mother

Mitochondrial inheritance

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Diseases passed by mitochondrial inheritance

MELAS

Leber’s hereditary optic neuropathy

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Mutations in single genes w/ large effects (high penetrance)

Mendelian disorders

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Trinucleotide involved in Huntington’s dse

CAG

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Trinucleotide involved in myoTonic dystrophy

CTG

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Trinucleotide involved in Fragike X syndrome

CGG

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Trinucelotid einvolved in Friedrich’s ataxia

GAA

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D/o of CT d/t defect in fibrillin-1; presents with skeletal, ocular changes (ectopia lentis), and CV changes (MVP, cystic medial necrosis)

Marfan syndrome

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What condition does cystic medial necrosis predispose to?

Aortic dissection

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Bilateral subluxation of the lens

Ectopia lentis

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D/O of CT d/t defect in fibrillar collagen (most commonly Type III)
S/Sx: hypermobile jts, stretchable skin

Ehlers-Danlos Syndrome

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Inherited d/o w/ mutation to gene encoding LDL receptor; high risk for premature atherosclerosis

Hypercholesterolemia

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Enzyme deficient in Tay-Sachs Disease

Hexosaminidase-a

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Involvement of Tay-Sachs Disease

CNS (MR)

Retina (cherry-red spot in macula)

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Elevated in lysosomes of Tay Sachs pts

GM2 gangliosides

Dse w/ lysosomal accumulation if sphingomyelinase

Niemann-Pick Disease

Difference b/w type A and B Niemann-Pick Disease?

Type B has no CNS involvement

Organs enlarged in Niemann-Pick disease

Spleen | Liver

Cytoplasmic bodies resembling concentric lamellated myelin figures in Niemann-Pick Disease

Zebra bodies

Difference b/w Tay-Sachs and Niemann-Pick Disease

Niemann-Pick Disease presents with hepatosplenomegaly

Most common lysosomal storage disorder

Gaucher Disease

Mutation in gene encoding what is affected in Gaucher's Disease

Glucocerebrosidase

Deficiencies of lysosomal enzymes involved in degradation of glycosaminoglycans

Mucopolysaccharidoses

Enzyme defect in Type I mucopolysaccharidoses (MPS)

a-L-iduronidase

Enzyme defect in Type II MPS

Iduronosulfate sulfatase

Enzyme defect in Type III (Sanfilippo) MPS

Heparan N-sulfatase | N-acetylglucosaminidase

Enzyme defect in Type IV (Morquio) MPS

N-acetylgalactosamine-6-sulfatase

Enzyme defect in Type V (Scheie) MPS

a-L-iduronidase

Enzyme defect in Type VI (Maroteaux-Lamy) MPS

N-acetylgalactosamine-4-sulfatase

Enzyme defect in Type VII (Sly) MPS

B-glucoronidase

Distended cells w/ clearing of the cytoplasm; seen in MPS

Balloon cells

Enzyme that converts hemogentistic acid to methylacetoacetic acid; deficient in ALKAPTONURIA

Homogentisic oxidase

Disease presenting w/ black urine, ochronosis (blue-black pigmentation on the ears, nose, cheeks) and pigment deposits in articular cartilages

Alkaptonuria

Unequal separation of chromosome in meiosis I; seen in Turner's and Down syndrome

Nondisjunction

Mitotic errors giving rise to >2 population of cells w/ diff chr complement

Mosaicism

Loss of portion of chromosome; seen in Cri du chat syndrome

Deletion

Transfer of chromosomal pts b/w nonhomologous chromosomes

Translocation

Trisomy 21

Down syndrome

Trisomy 13

Patau syndrome

Trisomy 18

Edward syndrome

P's of Patau

Polydactyly Cleft Palate HoloProsencephaly

Results of quadruple screen in Down's syndrome

Inc bHCG Inc inhibin A Dec AFP Dec estriol

UTZ finding in fetus w/ Down's syndrome

Increased nuchal translucency

Disease assoc w/ Down syndrome

Hirschsprung's disease Duodenal atresia Alzheimer disease ALL, AML

Microdeletion of long arm of chr 7; elfin facies and extreme friendliness

Williams syndrome

47 XXY, male hypogonadism, eunuchoid body shape

Klinefelter syndrome

Short stature, shield chest, webbed neck, Coarctation of the aorta

Turner syndrome

2nd most common genetic cause of MR; long face w/ large mandible, everted ears, macro-orchidism

Fragile X syndrome | X-men's Wolverine: extra large ears, jaws, testes

Microdeletion on paternal chr 15; hyperphagia, MR, hypotonia, hypogonadism

Prader-Willi syndrome

Microdeletion of maternal chr 15; happy puppet, wide based gait

Angelman syndrome