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Step 1 2019 First Aid Flashcards > Biochem FA - p56 - 64 Genetics > Flashcards

Biochem FA - p56 - 64 Genetics Flashcards

1
Q

Define codominance, ex/

A

Both alleles contribute to the phenotype of the heterozygote ; ex/ Blood groups, alpha anti trypsin def, HLA groups

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2
Q

Variable expressivity, ex/

A

Patients with the same genotype have varying phenotypes.

ex/ Neurofibromatosis

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3
Q

Incomplete penetrance, ex/

A

Not all individuals with a mutant genotype show the mutant phenotype.
ex. BRCA1 gene mutations do not always result in breast or ovarian cancer

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4
Q

Pleiotropy, ex/

A 
One gene contributes to multiple phenotypic effects.
Untreated phenylketonuria (PKU) manifests with light skin, intellectual disability, and musty body odor.
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5
Q

Anticipation

A

Increased severity or earlier onset of disease in succeeding generations.
Trinucleotide repeat diseases (eg, Huntington disease).

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6
Q

If parents and relatives do not have the disease, and the child does, what should you look for?

A

Gonadal mosaicism

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7
Q

patient with cafe au lait on one side of their bodies with ragged edges, bones replaced with collagen, and endocrine issues?

A

McCune Albright syndrome

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8
Q

What protein is activated in McCune Albright?

A

Gs protein

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9
Q

ex of locus heterogeneity?

A

albinism

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10
Q

What is allelic heterogeneity? ex?

A

Different mutations in the same locus producethe same phenotype.
ex/ β-thalassemia.

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11
Q

Define uniparental disomy

A

Offspring receives 2 copies of a chromosome from 1 parent and no copies from the other parent.

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12
Q

Describe the difference between heterodisomy and isodisomy?

A

HeterodIsomy (heterozygous) indicates a meiosis I error. IsodIsomy (homozygous) indicates a meiosis II error or postzygotic chromosomal duplication of one of a pair of chromosomes, and loss of the other of the original pair

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13
Q

In Hardy Weinberg law, how do we calculate frequency of allele A and a, and Aa?

A 
p^2 = freq of homozygosity for allele A
q^2 = freq of homozygosity for recessive allele a
2pq = freq of heterozygosity
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14
Q

How to calculate freq of x linked recessive disease in males and females?

A 
males = q
females = q^2
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15
Q

Define Imprinting

A

one gene copy is silenced by methylation, and only the other copy is expressed –>parent-of-origin effects

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16
Q

Difference in genetic errors of Prader Willi and Angelman syndrome?

A

In Prader Willi - maternally derived genes are silenced (imprinted), and Paternal allele is deleted or mutated
In Angelman - paternal derived UBE3A gene is silenced, and Maternal allele is deleted or mutated.

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17
Q

Sx of Prader Willi

A

hyperphagia, obesity, intellectual disability, hypogonadism, hypotonia

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18
Q

Sx of Angelman

A

inappropriate laughter (“happy puppet”), seizures, ataxia, severe intellectual disability

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19
Q

enzyme deficiences usually have what type of inheritence?

A

AR

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20
Q

What’s the probability that an unaffected individual with a sibling affected with AR disease is carrier?

A

Unaffected individual with affected sibling has 2/3 probability of being a carrier.

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21
Q

If you see a genetic chart, and there is no male-male transmission and the disease skips generations, what is mode of inheritance?

A

X linked recessive

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22
Q

On a genetic chart, an affected mother passes a disease to half her offspring and an affected father passes it on to all his daughters, but not his sons - what is his mode of inheritance?

A

X linked dominant

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23
Q

Ex of X linked dominant disease?

A

Hypophosphatemic rickets, Fragile X syndrome, Alport syndrome, Focal dermal hypoplasia

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24
Q

What mode of inheritance is only thru the mother?

A

Mitochondrial inheritance

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25
Q

Mode of inheritance of a disease that results in inc phosphate wasting at the proximal tubule?

A

X linked dominant - (Hypophospatemic rickets formerly known as vit D resistent rickets)

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26
Q

Mode of inheritance of disease with CGG trinucleotide repeat?

A

X linked dominant - Fragile X syndrome

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27
Q

Mode of inheritance of disease with myopathy, lactic acidosis, and CNS sx (stroke like episodes)?

A

Mitochondrial inheritance - MELAS syndrome

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28
Q

What causes the ragged red fibers of MELAS myopathy?

A

Muscle biopsy often shows “ragged red fibers” (due to accumulation of diseased mitochondria in the subsarcolemma of the muscle fiber).

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29
Q

subacute bilateral vision loss in a male teen - what disease and inheritance?

A

Leber hereditary optic neuropathy, mitochondrial inheritence

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30
Q

AD disease

A 
Achondroplasia, 
autosomal dominant polycystic kidney disease,
familial adenomatous polyposis, 
familial hypercholesterolemia,
hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome), 
hereditary spherocytosis, 
Huntington disease, 
Li-Fraumeni syndrome, 
Marfan syndrome, 
multiple endocrine neoplasias, 
myotonic muscular dystrophy, 
neurofibromatosis type 1 (von Recklinghausen disease), neurofibromatosis type 2, 
tuberous sclerosis, 
von Hippel-Lindau disease.
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31
Q

AR diseases

A

Albinism,
autosomal recessive polycystic kidney disease (ARPKD), cystic fibrosis,
Friedreich ataxia,
glycogen storage diseases,
hemochromatosis,
Kartagener syndrome,
mucopolysaccharidoses (except Hunter syndrome), phenylketonuria,
sickle cell anemia,
sphingolipidoses (except Fabry disease),
thalassemias,
Wilson disease

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32
Q

deletion of Phe508 on chromosome 7 leads to what disease?

A

Cystic Fibrosis

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33
Q

What does CFTR code for?

A

encodes an ATP-gated Cl− channel that secretes Cl− in lungs and GI tract, and reabsorbs Cl− in sweat glands

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34
Q

What’s the malfunction in CF?

A

Most common mutation = misfolded protein will be retained in RER and not transported to cell membrane, causing dec Cl− (and H2O) secretion;
Inc intracellular Cl− results in compensatory IncNa+ reabsorption via epithelial Na+ channels (ENaC) –> Inc H2O reabsorption –> abnormally thick mucus secreted into lungs and GI tract

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35
Q

Dx test for CF?

A

Inc Cl- concentration in a pilocarpine induced sweat test

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36
Q

How to screen newborn for CF?

A

Inc immunoreactive trypsinogen

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37
Q

Why does CF present with contraction alkalosis and hypokalemia?

A

Loss of ECF H20/Na+ thru sweat & renal K+/H+ wasting

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38
Q

Most common pulmonary infections for CF in childhood and adults?

A

Infancy and early childhood - S. aureus

adulthood - Pseudomonas

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39
Q

What causes reticulonodular pattern on chest xray and opacification of sinuses with CF?

A

Chronic bronchitis and bronchiectasis

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40
Q

GI issue in newborns with CF?

A

Meconium ileus

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41
Q

GI issues in adults with CF?

A

Pancreatic insufficiency, malabsorption with steatorrhea, fat-soluble vitamin deficiencies (A, D, E, K), biliary cirrhosis, liver disease

42
Q

Why is there fertility issues in CF?

A

Infertility in men (absence of vas deferens, spermatogenesis may be unaffected) and subfertility in women (amenorrhea, abnormally thick cervical mucus).

43
Q

Rx used to treat patients with Phe508 deletion? What’s their MOA?

A

combination of Lumacaftor (corrects misfolded proteins and improves their transport to cell surface)
Ivacaftor (opens Cl– channels –>improved chloride transport).

44
Q

What rx can slow disease progression in CF? What drug is used as an anti-inflammatory agent?

A

Ibuprofen; Azithromycin

45
Q

X linked recessive disorders?

A 
Ornithine transcarbamylase deficiency, 
Fabry disease, 
Wiskott-Aldrich syndrome, 
Ocular albinism, 
G6PD deficiency, 
Hunter syndrome, 
Bruton agammaglobulinemia, 
Hemophilia A and B, 
Lesch-Nyhan syndrome, 
Duchenne (and Becker) muscular dystrophy.

Oblivious Female Will Often Give Her Boys Her x-Linked Disorders

46
Q

What is lyonization?

A

Lyonization is X inactivation —one copy of female X chromosome forms a transcriptionally inactive Barr body. Female carriers variably affected depending on the pattern of inactivation of the X chromosome carrying the mutant vs normal gene

47
Q

Which females are more likely to have a x linked recessive disorder?

A

Females with Turner syndrome (45,XO) are more likely to have an X-linked recessive disorder.

48
Q

What is Gower’s sign?

A

patient uses upper extremities to help stand up.

49
Q

What type of mutation is seen in Duchenne’s muscular dystrophy?

A

frameshift or nonsense mutations

50
Q

What type of mutation is seen in Becker’s muscular dystrophy?

A

usually non frameshift deletions

51
Q

Difference in onset of Duchenne and Becker’s muscular dystrophy?

A

Duchenne’s mutation is more severe - onset <5 years old. Becker’s onset is adolesence or early adulthood

52
Q

Function of dystrophin?

A

Dystrophin helps anchor muscle fibers, primarily in skeletal and cardiac muscle. It connects the intracellular cytoskeleton (actin) to the transmembrane proteins α- and β-dystroglycan, which are connected to the extracellular matrix (ECM).

53
Q

Lab parameters increased in Duchenne?

A

Inc CK and aldolase

54
Q

Most common cause of death in Duchenne?

A

dilated cardiomyopathy

55
Q

Mode of inheritance of myotonic type I muscular dystrophy?

A

AD

56
Q

How does Duchenne’s present and progress?

A

Weakness begins in pelvic girdle muscles, leading to a waddling gait, and progresses superiorly.

57
Q

What is the genetic issue in myotonic type 1 muscular dystrophy?

A

. CTG trinucleotide repeat expansion in the DMPK gene –>abnormal expression of myotonin protein kinase

58
Q

Sx of myotonic type I muscular dystrophy?

A

myotonia, muscle wasting, cataracts, testicular atrophy, frontal balding, arrythmia

59
Q

Genetic mutation in Rett syndrome?

A

de novo mutation of MECP2 on X chromosome

60
Q

What are the symptoms of Rett syndrome and when do they appear?

A

usually appear between ages 1–4 and are characterized by regression (Retturn) in motor, verbal, and cognitive abilities; ataxia; seizures; growth failure; and stereotyped handwringing.

61
Q

Patient population of Rett syndrome

A

toddler girls, most boys will die in utero or shortly after birth

62
Q

Most common cause of inherited intellectual disability?

A

Fragile X

63
Q

1 & #2 cause of genetiically associated mental def?

A
  1. Downs 2. Fragile X
64
Q

Cardiac sx of fragile x?

A

systolic murmur with midsystolic click - mitral valve prolapse

65
Q

Sx/ of Fragile X

A

Big balls (post pubertal macroochidism), Long face, Large jaw, Big Ol everted ears, autism, mitral valve prolapse

66
Q

Trinucleotide repeat and mode of inheritance in Huntingtons

A

CAG; AD - Caudate has decACh and GABA

67
Q

Trinucleotide repeat and mode of inheritance in Myotonic dystrophy

A

CTG; AD - Cataracts, Toupee (early balding in men), Gonadal atrophy

68
Q

Trinucleotide repeat and mode of inheritance in Fragile X

A

CGG; XD - Chin (protruding), Giant Gonads

69
Q

Trinucleotide repeat and mode of inheritance in Freidrich ataxia

A

GAA; AR

70
Q

Why is Down’s associated with Alzheimers?

A

Associated with early-onset Alzheimer disease bc chromosome 21 codes for amyloid precursor protein

71
Q

What issue in Downs is due to failure of neural crest cell migration?

A

Hirschsprung - Think Shits Sprung - as in explosive expulsion of feces “squirt sign”

72
Q

Signs of GI issue in Down’s

A

Presents with bilious emesis, abdominal distention, and failure to pass meconium within 48 hours (Hirschsprung)

Also duodenal atresia

73
Q

What do you look for in 1st trimester as sign of Downs? 2nd trim?

A

First-trimester ultrasound commonly shows Incnuchal translucency and hypoplastic nasal bone.
2nd trim - Markers for Down syndrome are HI up: Inc hCG, Inc inhibin. (dec AFP and Estriol)

74
Q

Physical sx of Down’s

A

flat facies, prominent epicanthal folds, single palmar crease, incurved 5th finger, gap between 1st 2 toes

75
Q

5 As of Down’s?

A

The 5 A’s of Down syndrome: ƒ Advanced maternal age ƒ Atresia (duodenal) ƒ Atrioventricular septal defect ƒ Alzheimer disease (early onset) ƒ AML/ALL

76
Q

Why can Down patient present with wide, fixed split S2? What are other sx assoc with the underlying issue?

A

ASD (Atrial septal defect) - O2 saturation INCin RA, RV, and pulmonary artery

77
Q

Most common cause of Down?

A

95% of cases due to meiotic nondisjunction (meiosis I)

78
Q

Sx of Edwards syndrome?

A 
PRINCE Edward—
Prominent occiput, 
Rocker-bottom feet, 
Intellectual disability, 
Nondisjunction, 
Clenched fists (with overlapping fingers),
low-set Ears
79
Q

1st and 2nd trimester screening for Edwards?

A

1st - dec B-hCG

2nd - Dec everything - BhCG, Inhibin A, AFP, Estriol

80
Q

When do you see inc AFP

A

neural tube defect

81
Q

Findings in Patau?

A

severe intellectual disability, rockerbottom feet, microphthalmia, microcephaly, cleft liP/Palate, holoProsencephaly, Polydactyly, cutis aPlasia, congenital heart (Pump) disease, Polycystic kidney disease

82
Q

Cri du Chat syndrome presents with what type of murmur? Inc or dec with hand grip and squatting?

A

holosystolic harsh sounding murmur, will inc with hand grip and squatting = VSD

83
Q

genetic issue with Cri du chat?

A

Congenital deletion on short arm of chromosome 5 (46,XX or XY, 5p−).

84
Q

Findings of Cri du chat?

A

microcephaly, moderate to severe intellectual disability, high-pitched crying/ meowing, epicanthal folds, cardiac abnormalities (VSD).

85
Q

Genetic issue in Williams syndrome?

A

Congenital microdeletion of long arm of chromosome 7 ( william has 7 letters)

86
Q

Findings in Williams syndrome

A

distinctive “elfin” facies, intellectual disability, hypercalcemia, well-developed verbal skills, extreme friendliness with strangers, cardiovascular problems (eg, supravalvular aortic stenosis, renal artery stenosis). Think Will Ferrell in Elf.

87
Q

Diseases from Chromosome 3

A

von Hippel-Lindau disease, renal cell carcinoma

88
Q

Diseases from Chromosome 4

A

ADPKD (PKD2), achondroplasia, Huntington disease

89
Q

Diseases from Chromosome 5

A

Cri-du-chat syndrome, familial adenomatous polyposis

90
Q

Diseases from Chromosome 6

A

Hemochromatosis (HFE)

91
Q

Diseases from Chromosome 7

A

Williams syndrome, cystic fibrosis

92
Q

Diseases from Chromosome 9

A

Friedreich ataxia, tuberous sclerosis (TSC1)

CML/ALL t(9;22)

93
Q

Diseases from Chromosome 11

A

W11ms tumor, β-globin gene defects (eg, sickle cell disease, β-thalassemia), MEN1

Mantle cell t(11:14) Marginal cell lymphoma t(11:18)

94
Q

Diseases from Chromosome 13

A

Patau syndrome, Wilson disease, retinoblastoma (RB1), BRCA2

95
Q

Diseases from Chromosome 14

A

Burkitts t(8;14), Mantle Cell t(11;14), Follicular t(14;18)

96
Q

Diseases from Chromosome 15

A

Prader-Willi syndrome, Angelman syndrome, Marfan syndrome

APL (type M3 AML) = t(15;17)

97
Q

Diseases from Chromosome 16

A

ADPKD (PKD1), α-globin gene defects (eg, α-thalassemia), tuberous sclerosis (TSC2)

98
Q

Diseases from Chromosome 17

A

Neurofibromatosis type 1, BRCA1, TP53

99
Q

Diseases from Chromosome 18

A

Edwards syndrome

Follicular lymphoma t(14:18)

100
Q

Diseases from Chromosome 21

A

Down syndrome

101
Q

Diseases from Chromosome 22

A

Neurofibromatosis type 2, DiGeorge syndrome (22q11)

CML/ALL t(9;22)

102
Q

Diseases from Chromosome X

A

Fragile X syndrome, X-linked agammaglobulinemia, Klinefelter syndrome (XXY)

Step 1 2019 First Aid Flashcards (63 decks)

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