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Biochemistry First Aid USMLE Step 1 > Genetics > Flashcards

Genetics Flashcards

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USMLE® Step 1 flashcards
1
Q

Autosomal Dominant Nervous Diseases

A
  • Huntington, Neurofibromatosis, Myotonic Dystrophy, Tuberous Sclerosis
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2
Q

Autosomal Dominant Urinary Disease

A

Polycystic Kidney Disease

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3
Q

Autosomal Dominant GI Disease

A

Familial Polyposis coli

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4
Q

Autosomal Dominant Hematopoietic Diseases

A
  • Hereditary sperocytosis and von Willebrand Disease
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5
Q

Autosomal Dominant Skeletal Disease

A
  • Marfan Syndrome, Ehlers-Danlos Syndrome (some variants), Osteogenesis Imperfecta, Achondroplasia
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6
Q

Autosomal Dominant Metabolic Disease

A
  • Familial Hypercholesterolemia, Acute Intermittent Porphyria
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7
Q
  • Faulty collagen synthesis due to irregular cross-linking of collagen fibers, types I or V most frequent in severe disease.
  • Causes hyper extensible skin, tendency to bleed (easy bruising), and hyper mobile joints.
  • May be associated with joint dislocation, berry aneurysms or organ rupture.
A

Ehlers-Danlos Syndrome

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8
Q
  • Fibrillin-1 gene mutation -> connective tissue disorder affecting EYES, SKELETON, and HEART.
  • Presents tall with long extremities, pectus excavatum, hyper mobile joints, long-tapering fingers/toes, floppy mitral valve, Mitral Valve Prolapse (most common), Subluxation of Lenses.
A

Marfan Syndrome (Big Tall Blind Guy with Heart Problems)

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9
Q
  • Elevated LDL due to defective or absent LDL receptor.
  • Present with severe athersclerosis early on, TENDON XANTHOMAS (Achilles), Corneal Arcus.
  • MI before age 20.
A

Familial Hypercholesterolemia (hyperlipidemia type IIA)

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10
Q

X-linked Recessive Disorders

Be Wise, Fool’s GOLD Heeds Silly HOpe

A
  • Bruton’s Agammaglobulinemia
  • Wiskott-Aldrich Syndrome
  • Fabry’s Disease
  • G6PD Deficiency
  • Ocular Albinism
  • Lesch-Nyhan Syndrome
  • Duchenne’s (and Becker’s) muscular Dystrophy
  • Hunter’s Syndrome
  • Hemophilia A and B
  • Ornithine Transcarbamoylase Deficiency
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11
Q

Lysosomal Storage Diseases (Fat Guys kNow Their Kakes and Meats, How Happy)

A
  • Fabry’s, Gaucher’s , Niemann-Pick, Tay-Sachs, Krabbe’s, Metachromatic Leukodystrophy, Hurler’s, and Hunter’s.
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12
Q
  • Deficient Hexoaminidase A (alpha subunit) leads to GM2 Ganglioside accumulation. Autosomal Recessive
A

Tay-Sachs Disease

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13
Q
  • Deficient Sphingomyelinase leads to Sphingomyelin accumulation in mononuclear phagocytes. Autosomal Recessive.
  • Type A more common
A

Niemann-Pick Disease

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14
Q
  • Deficient Glucocerebrosidase leads to Glucocerebroside accumulation. Autosomal Recessive.
  • Most common.
A

Gaucher Disease w/Gaucher’s Cells

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15
Q
  • Deficient Iduronate Sulfatase leads to Heparan Sulfate/Dermatan Sulfate Accumulation. X-Linked.
A

Hunter’s Syndrome

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16
Q
  • Deficient alpha-L-iduronidase leads to Heparan Sulfate and Dermatan Sulfate accumulation. Autosomal Recessive
A

Hurler’s Syndrome

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17
Q
  • No man picks his nose with his sphinger!
  • Tay-SaX lacks heXosaminidase.
  • Hunters see clearly and aim for the X.
A

Nieman-Pick accumulates sphingomyelin.

  • Tay-Sachs lacks Hexosaminidase A.
  • Hunter’s Syndrome does not have corneal clouding and is X-Linked.
18
Q

Glycogen Storage Diseases (Very Poor Carbohydrate Metabolism

A
  • Von Gierke’s Disease (Type I)
  • Pompe’s Disease (Type II)
  • Cori’s Disease (Type III)
  • McArdle’s Disease (Type IV)
19
Q
  • Autosomal Recessive deficiency of Glucose-6-phosphatase.

- Present w/ sever fasting hypoglycemia, increased glycogen in liver, increased blood lactate, and hepatomegaly.

A

Von Gierke’s Disease (Type I)

20
Q
  • Autosomal Recessive deficiency of Lysosomal alpha-1,4-glucosidase (acid maltase)
  • Cardiomegaly and systemic findings lead to early death.
A

Pompe’s Disease (Type II)

-Pompe’s Trashes the Heart

21
Q
  • Autosomal Recessive deficiency of glycogen debranching enzyme alpha-1,6-glucosidase.
  • Mild form of Type I with normal blood lactate. Gluconeogenesis is intact.
A

Cori’s Disease (Type III)

22
Q
  • Autosomal Recessive deficiency of Skeletal Muscle Glycogen Phosphorylase.
  • Increased glycogen in muscle, but cannot break it down, leading to painful muscle cramps, myoglobinuria with strenuous exercise.
A

McArdle’s Disease (Type IV)

- McCardle’s = Muscle

23
Q
  • Congenital Deficiency of homogentisic acid oxidase in degradative pathway of Tyrosine (and Phenylalanine) to fumarate. Autosomal Recessive and Benign.
A

Alkaptonuria (Ochronosis)

24
Q
  • Trisomy 13 (Puberty @ 13)
  • Findings: severe MR, rocker-bottom feet, microphthalmia, microcephaly, cleft liP/Palate, holoProsencephaly, Polydactyly, congenital heart disease. Death within a year.
  • Prego quad screen shows decreased free beta-hCG, decreased PAPP-A and increased nuchal translucency.
A

Patau’s Syndrome

25
Q
  • Trisomy 18 (Election @ 18)
  • Findings: Severe MR, rocker-bottom feet, micrognathia (small jaw), low-set Ears, clenched hands, prominent occiput, congenital heart disease. Death within a year.
  • Prego quad screen shows decreased alpha-fetoprotein, decreased beta-hCG, decreased estriol, normal inhibin A.
A

Edward’s Syndrome

26
Q
  • Trisomy 21 (Drinking age: 21): Most common viable chromosomal disorder and Most common cause of genetic MR.
  • MR, flat facies, prominent epicanthal folds, simian crease, gap between first two toes, duodenal atresia, congenital heart disease (most common is ostium primum-type ASD).
  • Associated w/increased risk of ALL and Alzheimer’s disease (>35 years of age)
A

Down Syndrome Chromosome and Findings

27
Q

Causes of Down Syndrome and Prego Quad Screen Results

A
  • 95% due to meiotic nondisjunction of homologous chromosomes - advanced maternal age.
  • 4% due to Robertsonian translocation
  • Prego Quad shows decreased alpha-fetoprotein, increased beta-hCG, decreased estriol, increased Inhibin A and increased nuchal in first trimester translucency.
28
Q
  • Aberrant Development of 3rd and 4th Branchial Pouches due to micro deletion at chromosome 22q11.
  • DiGeorge Syndrome: Thymic, parathyroid, and Cardiac Defects
  • Velocardiofacial Syndrome: Palate, facial and cardiac defects.
A

22q11 Deletion Syndromes (Catch-22)

29
Q

Trinucleotide Repeat Expansion Diseases (Try Hunting for My Fried Eggs (X)) and (X-Girlfriend’s First Aid Helped Ace My Test)

A
  • Huntington’s Disease, Myotonic Dystrophy, Friedreich’s ataxia, Fragile X syndrome
  • Fragile X Syndrome = (CGG)
  • Friedreich’s Ataxia = (GAA)
  • Huntington’s Disease = (CAG)
  • Myotonic Dystrophy = (CTG)
30
Q
  • X-linked defect affecting the methylation and expression of the FMR1 (Familial Mental Retardation-1) gene. Trinucleotide repeat of CGG.
  • Findings: macroorchidism (eXtra large testes), long face with large jaw, large everted ears, autism, and mitral valve prolapse.
A

Fragile X Syndrome

31
Q
  • Paternal (DAD’s) allele is NOT expressed.
  • Findings: MR, hyperphagia, obesity, hypogonadism, hypotonia (leads us to believe that it is the mother’s gene that makes us eat tons, have no balls, and be weak).
A

Prader-Willi Syndrome

32
Q
  • Maternal (Mom’s) allele is NOT expressed.
    Findings: MR, seizures, ataxia, inappropriate laughter. (Shows us that it really is the Father’s gene that makes us inappropriate)
A

AngelMan’s Syndrome

33
Q
  • 46, XXY: Male
  • Dysgenesis of seminiferous tubules -> decreased inhibin -> increased FSH.
  • Abnormal Leydig cell function -> decreased testosterone -> increased LH -> increased estrogen.
  • Findings: Testicular Atrophy (small balls), eunuchoid body shape, tall, long extremities, gynecomastia, female hair distribution. Developmental Delay with presence of inactivated X chromosome (Barr body).
A

Klinefelter’s Syndrome

34
Q

46, XO: Female. (Hugs and Kisses XO from Tina Turner)

- Menopause before menarche. Decreased estrogen leads to increased LH and FSH.

A

Turner’s Syndrome Chromosomal Abnormalities

35
Q
  • Short Stature due to loss of both copies of short stature homeobox gene (SHOX) on the X chromosome.
  • Ovarian dysgenesis (streak ovary with infertility), shield chest, bicuspid aortic valve, defects in lymphatics leading to webbed neck (cystic hygroma), and lymphedema in feet and hands, pre ductal coarctation of the aorta, horseshoe kidney, and dysgerminoma.
  • Most common cause of primary amenorrhea. No Barr Body.
A

Turner’s Syndrome Findings

36
Q
  • Present with prog. neurodegeneration, developmental delay, cherry-red spot on macula (due to lipid accum. in retinal ganglion cells), lysosomes with onion skin, no hepatosplenomegaly.
A

Tay-Sachs Disease

37
Q
  • Prog. neuodegeneration, hepatosplenomegaly, cherry-red spot on macula, foam cells (lipids accum. in mononuclear phagocytes)
A

Niemann-Pick Disease

38
Q
  • Present w/ Hepatosplenomegaly, aseptic necrosis, bone crises, macrophages that look like crumpled tissue paper.
A

Gaucher’s Disease w/ Gaucher Cells

39
Q
  • Present w/ dark blue-black connective tissue (ears, nose, and cheeks), brown pigmented sclera, urine turns black on prolonged exposure to air. Debilitating arthralgias due to homogentisic acid toxicity to cartilage.
A

Alkaptonuria (Ochronosis)

40
Q

Signs of 22q11 Deletion

A
  • CATCH-22
  • Variable presentation including (CATCH) Cleft Palate, Abnormal Facies, Thymic aplasia -> T-cell deficiency, Cardiac Defects, Hypocalcemia secondary to parathyroid aplasia.
41
Q
  • Present w/ Developmental Delay, gargoylism, airway obstruction, hepatosplenomegaly, aggressive behavior, and no corneal clouding!
A

Hunter’s Syndrome

42
Q
  • Present w/ Developmental Delay, gargoylism, airway obstruction, corneal clouding, and hepatosplenomegaly.
A

Hurler’s Syndome

Biochemistry First Aid USMLE Step 1 (6 decks)

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