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USMLE > Genetics > Flashcards

Genetics Flashcards

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USMLE® Step 1 flashcards
1
Q

Pleiotropy

A

more than one phenotype for a given genetic mutation (ie PKU)

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2
Q

Imprinting

A

Difference in phenotype depend on whether mutation is maternal or paternal origin; Prader Willi and Angelman’s syndromes

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3
Q

Dominant negative mutation

A

heterozygous mutation that exerts a dominant effect by producing a nonfunctional protein (ie. A nonfunctional transcription factor that still happens to bind DNA so acts to block wild type transcription factor) that prevents normal gene product from doing its job (another example is marfan’s fibrillin mutation disrupts normal fibrillin)

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4
Q

Linkage disequilibrium

A

When two alleles occur together more often than would be expected by chance alone.

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5
Q

Mosaicism

A

Loss of genetic information during mitosis; Lyonization, Mutation in the embryonic precursor of the bone marrow stem cell

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6
Q

Locus heterogeneity

A

One phenotype from produced by different loci mutations; Marfan’s syndrome, MEN 2B, albinism, homocystinuria

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7
Q

Heteroplasmy

A

Presence of normal and mutated mtDNA results in variable expression of mito inherited disease

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8
Q

Uniparental disome

A

Offspring receive 2 copies from one parent and none from the other.

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9
Q

Prader-Willi syndrome

A

Normally inactivated maternal allele is active. Paternal allele is either deleted or abnormally silenced or has uniparental disomy from mother. Chr 15; Mental retardation, hyperphagia, obesity, hypogonadism, hypotonia

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10
Q

Angelman’s syndrome

A

Normally inactivated paternal allele is active. Maternal allele is either deleted, inactivated, or uniparental disomy of father; Mental retardation, seizures, ataxia, inappropriate laughter

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11
Q

Patau syndrome

A

nondisjunction 47, XX, +13; arises during maternal meiosis I; Early defect in prechordal mesoderm development. Midface, eye, forebrain most affected: Cleft lip/palate, microphthalmia, microcephaly, holoprosencephaly, absent olfactory nerve, polydactyly, rocker-bottom feet, PDA, VSD, PCKD, Omphalocele or umbilical hernia

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12
Q

Causes of Down syndrome

A

Meitic nondisjunction of Chr 21 almost always of maternal origin; unbalanced robertsonian translocation where extra arm of chromosome 21 is attached to another chromosome; mosaicism where patients have a normal cell germ line and a trisomy germ line.

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13
Q

Hemophilia B/A Disorder’s Inheritance is

A

X-linked recessive

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14
Q

Huntington inheritance

A

autosomal dominant

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15
Q

Lesch-Nyhan inheritance

A

X-linked recessive

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16
Q

Leber hereditary optic neuropathy inheritance

A

mitochondrial

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17
Q

t(8;14)

A

Burkitt’s lymphoma; myc protooncogene is moved to 14 in front of immunoglobulin heavy chain.

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18
Q

t(9;22)

A

CML; bre-abl

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19
Q

t(11;14)

A

Mantle cell lymphoma; Activation of cyclin D gene

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20
Q

13q deletion

A

CLL association

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21
Q

t(15;17)

A

AML M3

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22
Q

3p deletion

A

Von Hippel-Lindau; autosomal dominant; medullary, cerebellar, and retinal hemangioblastomas; pheochromocytomas; pancreatic, hepatic, renal cysts; renal cell carcinoma

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23
Q

Fragile X gene

A

X-linked defect affecting methylation and expression of FMR1 gene. Trinucleotide repeat disorder of CGG resulting in hypermethylation of cytosine bases and gene inactivation

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24
Q

Cystic Fibrosis Mutation

A

Autosomal Recessive; Chromosome 7; deletion of Phe 508, mutation causes abnormal protein folding so it is degraded before even reaching the membrane. Normally the channel is activated by cAMP signaling and ATP gated

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25
Q

Cystic hygromas

A

seen mostly in Turner’s patients; tumor mostly located on neck and seen at birth. Swelling of the hands and feet is another manifestation. Swelling may decrease with age

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26
Q

Congenital Hypothyroidism

A

lethargic, poor feeding, prolonged jaundice, constipation, hypotonia, pale cool skin, myxedema; Umbilical Hernia, increased risk of heart defects. T4 is essential for myelination

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27
Q

Trisomy 21 genetic abnormalities

A

Nondisjunction due to a failure of homologous chromosomes to separate in meiosis I or sister chromatids to separate during meiosis II.

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28
Q

Pick bodies

A

eosinophilic intracytoplasmic inclusions in cortical neurons in Pick disease

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29
Q

Lewy Bodies

A

inclusions that contain neurofilaments seen in neurons of substantia nigra in Parkinson

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30
Q

Conditions associated with Downs

A

AML, ALL, Parkinson, Hirschsprungs and Duodenal atresia

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31
Q

Neurofibrillary tangles

A

beta-amyloid accumulation in brain tissue and vessel walls.

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32
Q

Inhibition of gene expression in Huntington disease occurs via

A

CAG repeats lead to abnormal hintingtin protein which decreases the expression of other genes by inhibiting their transcription via hypermethylation of histones.

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33
Q

Reassortment

A

changes in genomic composition that occur when host cells are co-infected with two segented viruses that exchange whole genome segments. Can cause sudden alterations in the surface antigens of viral progeny

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34
Q

Recombination

A

exchange of genes between two chromosomes (dsDNA) by crossing over within homologous regions.

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35
Q

Transformation

A

uptake of naked DNA by prokaryotic or eukaryotic cell.

36
Q

Interference

A

inhibition by one virus of the replication and or release of a second virus that is infecting the same cell.

37
Q

G6PD deficiency inheritance

A

X-linked Recessive

38
Q

t(14;18)

A

Follicular lymphoma, Bcl-2

39
Q

ErbB2, HER2, neu

A

same name for epidermal growth factor receptor which is overexpressed in many booby cancers

40
Q

Sturge-Weber Syndrome

A

vascular disorder characterized by facial port-wine stain and leptomeningeal angioma

41
Q

NF1

A

chr. 17, autosomal dominant. Café au lait, neurofibromas, optic nerve gliomas, Lisch nodules, bony abnormalities; meningiomas, gliomas, pheochromocytomas.

42
Q

Mitochondrial inheritable diseases

A

Leber Hereditary optic neuropathy -> bilateral vision loss; Myoclonic epilepsy with ragged-red fibers -> myoclonic seizures and myopathy associated with exercise; Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS)

43
Q

Early-onset alzheimer disease

A

associated with APP (Chr 21) and Presenilin 1 and 2

44
Q

Late-Onset alzheimer disease

A

Associated with apolipoprotein E4

45
Q

Kartagener inheritance

A

Autosomal recessive microtubular defect

46
Q

Tuberous Sclerosis inheritance

A

autosomal dominant

47
Q

Friedrich’s ataxia inheritance

A

autosomal recessive

48
Q

Marfan syndrome

A

autosomal dominant

49
Q

Kallmann syndrome

A

failure of GnRH-secreting neurons to migrate from olfactory placode to hypothalamus; mutation in KAL-1 gene or FGF-Receptor 1 gene. Present with hypogonadism and anosmia, delayed puberty at presentation, Testes are small.

50
Q

Xeroderma pigmentosa iheritance

A

DNA excision repair defect that is Autosomal Recessive

51
Q

Bloom syndrome

A

Autosomal recessive

52
Q

Fanconi anemia

A

autosomal recessive

53
Q

Klinefelter syndrome is inherited through

A

an extra sex chormosome acquired due to meiotic nondisjunction during gametogenesis. XXY

54
Q

Androgenic alopecia

A

polygenic inheritance with variable penetrance.

55
Q

Common conditions with polygenic inheritance

A

Androgenetic alopecia, epilepsy, ischemic heart disease, schizophrenia, glaucoma, HTN, malignancy, Type 2 DM

56
Q

Cardiovascular associations with Downs, digeorge, Freidrich’s ataxia, Marfan, and Tuberous sclerosis

A

Down: endocardial cushion defects; DiGeorge, ToF and interrupted aortic arch; Freidrich’s ataxia, hypertrophic cardiomyopathy; Marfan, medial necrosis of aorta; Tuberous sclerosis, rhabdomyoma

57
Q

ADPKD

A

AD, PKD1 [integral membrane protein, signal transducer; renal tubular development] mutation on Chr 16; berry aneurysms, mitrial valve prolapse

58
Q

FAP

A

Familial adenomatous polyposis; Chromosome 5, APC gene (mismatch repair) Autosomal dominant

59
Q

Familial hypercholesterolemia (IIA)

A

AD; defective or absent LDL receptor; high LDL; major atherosclerosis, xanthomas etc.

60
Q

Osler-Weber-Rendu (Hereditary hemorrhagic telangiectasia)

A

AD; Blood vessel disorder with telangiectasia epistaxis, skin discoloration and AVMs

61
Q

Hereditary Spherocytosis

A

AD; spectrin or ankyrin defect; increased MCHC

62
Q

Huntington disease

A

AD; Chromosome 4; CAG

63
Q

Marfan

A

AD

64
Q

MEN syndrome

A

AD; 2A and 2B associated with Ret gene

65
Q

NF2

A

chromosome 22; AD; mutation in merlin; bilateral acoustic schwannomas; juvenile cataract

66
Q

von Hippel Lindeau

A

AD; deletion of VHL on Chr 3; constitutive expression of HIF that activates angiogenic growth factors

67
Q

cystic fibrosis

A

AR

68
Q

Glycogen storage diseases

A

AR

69
Q

Hemochromatosis

A

AR

70
Q

Mucopolysaccharidosis

A

AR (except Hunter’s - X-linked)

71
Q

PKU

A

AR

72
Q

Sickle cell

A

AR

73
Q

Sphingolipidoses

A

AR (except Fabry’s - X-linked)

74
Q

Thalassemias

A

AR

75
Q

Bruton’s agammaglobulinemia

A

X-linked recessive

76
Q

Wiskott-Aldrich

A

X-linked recessive

77
Q

Fabry’s

A

X-linked recessiv

78
Q

G6PD

A

X-linked recessive

79
Q

Ocular albinism

A

X-linked recessive

80
Q

Lesch-Nyhan

A

XR

81
Q

Duchenne’s and Becker’s MD

A

XR

82
Q

Hunter’s Syndrome

A

XR

83
Q

Hemophilia a and b

A

XR

84
Q

Robertsonian translocation

A

13, 14, 15, 21, 22; long arms of two acrocentric chromosomes fuse at centromere. Can be balanced or cause trisomy

85
Q

Microdeletion

A

cri du chat = short arm of 5. microcephaly, retardation, high pitched crying, epicanthal fold, VSD; Williams syndrome = microdeletion on Chr 7, elfin facies, retardation, hypercalcemia (high vit D sensitivity), well developed verbal skills, extreme friendliness with strangers

USMLE (14 decks)

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