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USMLE1 - Biochemistry > 3. Genetics > Flashcards

3. Genetics Flashcards

1
Q

Can a disorder be congential but not hereditary?

A

Yes! congenital simply means “born with”- hereditary is familial

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2
Q

what disease is associated with chromosome 15?

A

Imprinting Dx’s: prader Willi and Angelmann

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3
Q

what disease is associated with chromosome 16?

A

APCKD

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4
Q

what disease is associated with chromosome 5?

A

Familial Adenomatous Polyposis (APC gene)

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5
Q

what disease is associated with chromosome 4?

A

Hungtington

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6
Q

what disease is associated with chromosome 17?

A

NF1

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7
Q

what diseases are associated with chromosome 22?

A

NF2, DiGeorge/Velocardiofacial syndromes

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8
Q

what disease is associated with chromosome 3?

A

VHL (Von Hippa Lindau)

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9
Q

what disease is associated with chromosome 7?

A

Cystic Fibrosis (CFTR gene)

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10
Q

what disease is associated with chromosome 21?

A

Down’s Syndrome

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11
Q

what disease is associated with chromosome 18?

A

Edwards

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12
Q

what disease is associated with chromosome 13?

A

Pataus

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13
Q

what type of disorders are associated with chromosomes 13,14,15,21,22?

A

Robertsonian translocations

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14
Q

what disease is associated with chromosome 5?

A

Cri du Chat

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15
Q

what disease is associated with chromosome 7?

A

Williams

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16
Q

what disease is associated with chromosome 13?

A

Rb

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17
Q

Give an example of codominance.

A

Blood group types

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18
Q

With what type of inheritance is variable expression and incomplete penetrance associated with? Give an example of each.

A

Autosomal Dominant; NF1 and mit. diseases (variable expression), ?

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19
Q

What is Pleiotropy? What is the opposite of Pleiotropy? Give an example of each.

A

1 gene has greater than 1 phenotypic effect; locus heterogeneity (many different mutations can cause the same phenotype); PKU; albinism, deafness, Marfanoid habitus (Marfans, MEN 2B, homocystinuria)

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20
Q

what 3 genetic disorders can cause Marfanoid habitus?

A

marfans, homocystinuria, MEN 2B

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21
Q

What is imprinting disease? Give 2 examples

A

When the disease manifestation depends on from who the gene deletion was inherited from d/t methylation that occurs; Prader Willi and AngelMann

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22
Q

What type of diseases exhibit anticipation?

A

Trinucleotide expansion diseases

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23
Q

What is loss of heterozygosity? name an example.

A

When the 2nd hit of the allele is what causes the disease; sporadic retinoblastoma

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24
Q

T/F Loss of heterozygosity is the rule with oncogenes.

A

False! This is the rule for tumor suppressor genes (p53, Rb, BAX)

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25
Q

T/F Sporadic Retinoblastoma results in unilateral ocular tumor in children with osteosarcomas.

A

False- first part of question is right- sporadic is unilateral, but only familial is associated with osteosarcomas (Rb mutation is in all cells!)

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26
Q

Name two reasons why mosaicism might occur.

A

lyonization; nondisjunction in mitotic divisions during embryonic period

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27
Q

What is heteroplasmy?

A

presence of normal and mutated mtDNA (like mosaicism except in mit)

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28
Q

what is uniparental disomy? give an example of a disease it can cause.

A

when child gets two chromosomes from one parent; imprinting dx

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29
Q

T/F in all recessive diseases, prevalence of disease =q^2

A

false! in x linked, in males, prevalence is = q

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30
Q

With what tool are Prader Willi and Angelman diagnosed?

A

FISH

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31
Q

what is imprinting?

A

when one allele on a gene is only expressed and the other is methylated/inactivated; during gametogenesis one of the alleles is methylated because the gamete from the other sex will provide those characteristics for the child

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32
Q

what disease manifestations result in Prader Willi syndrome? is the deletion a result from the father or mothers chromosome?

A

mental retardation, obesity, short stature, hypogonadism, hypotonia, hyperphagia; father

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33
Q

what disease manifestations result in AngelMan syndrome? is the deletion a result from the father or mothers chromosome?

A

mental retardation, excessive laughter, seizures, ataxia, “happy puppet”

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34
Q

What type of proteins have AD mode of inheritance?

A

structural (constitutively active)

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35
Q

T/F AD disease present early

A

false! usually present late

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36
Q

T/F AD diseases are usually pleiotropic

A

True!

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37
Q

T/F AR disease are usually enzymatic

A

True!

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38
Q

T/F AR disease is usually not very severe, or less so than AD at lease

A

False! opposite

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39
Q

T/F heterozygous females in X linked recessive disease are not affected

A

false! can be d/t lyonization

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40
Q

T/F daughters of Xlinked recessive diseased fathers are all carriers

A

TRUE

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41
Q

T/F daughters of Xlinked dominant diseased fathers are all carriers

A

false- all are diseased!

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42
Q

What are two examples of X linked Autosomal Dominant disease?

A

hypophosphatemia rickets and Alports

43
Q

What is hypophosphatemia rickets? Can it be treated with Vit D?

A

In ability to reabsorb phosphate from renal tubular cells results in osteomalacia due to defective bone mineralization; no

44
Q

T/F All offspring of affected males with a mit disease can show disease.

A

False- none!

45
Q

what is the function of mitDNA?

A

encode enzymes for oxphos mit reactions

46
Q

Why do mitochondrial diseases exhibit variable expression?

A

heteroplasmy

47
Q

What are ragged red fibers?

A

collections of abnormal mit collecting under sarcolemmal membranes and results in distortion of myofibrils

48
Q

Other than ragged red fibers and lactic acidosis, what else is common in mit myopathies?

A

neurologic lesions and cardiomyopathies (ox phos!)

49
Q

What is the inheritance of myoclonic epilepsy?

A

mitochondrial inheritance

50
Q

What is lebers hereditary optic neuropathy? what is the main clinical symptom? and what is its mode of inheritance?

A

degeneration of retinal ganglion cells and axons; acute loss of central vision; mit. inheritance

51
Q

what is achondroplasia? what type of inheritance?

A

cell signaling defect in FGF receptor resulting in dwarfism and short limbs with normal head and trunk; AD

52
Q

T/F achondroplasia is associated with advanced maternal age

A

False- paternal

53
Q

T/F APCKD can be unilateral.

A

FALSE

54
Q

What else becomes cystic often in APCKD? other than cystic presentations what else do APCKD patients present with?

A

liver; berry aneurysms (d/t hypertension!), and mitral valve prolapse

55
Q

what inheritance pattern is Type IIA hypercholesterolemia? do heterozygotes present with disease? do homozygotes present?

A

AD: yes! most common presentation; very rare (700 mg/dl cholesterol level!)

56
Q

what is the inheritance pattern of hereditary hemorrhagic telangiectasia or Olser Weber Rendu Syndrome? What is it?

A

AD; disorder of blood vessels that results in telangietasias, skin discolorations, and AVMs (arteriovenous malformations)

57
Q

what is a telangiectasia? where can they be found?and what is a common result of them?

A

dilated capillaries and veins; skin, mucous membranes, GI, resp, urinary tracts; rupture and can cause epistaxis, hemorrhage, GI bleeding

58
Q

What is the inheritance pattern of hereditary spherocytosis?

A

AD

59
Q

what is the pathogenesis of Huntingtons disease?

A

gain of function gene after expansion results in overproduction of huntingtin protein that in overproduction results in toxicity to neurons in the caudate–> caudate atrophy and decreased levels of GABA and Ach

60
Q

what are the clinical symptoms of Huntingtons disease? when does it present?

A

depression, progressive dementia, choreiform movements; between the ages of 20 and 50

61
Q

What is the mode of inheritance of Marfans?

A

AD

62
Q

what is the mode of inheritance of Huntingtons?

A

AD (trinucleotide expansion is not a mode of inheritance)

63
Q

what are the clinical symptoms of Marfans?

A

HEART, SKELETON, and EYES: arachnodactyly, long limbs, cystic medial necrosis of aorta resulting in aneurysms (and eventual dissection), floppy mitral valve (prolapse and regurg!), subluxation of lens

64
Q

what is the mode of inheritance for the multiple endocrine neoplasias?

A

AD

65
Q

With what gene are MEN 2A and 2B associated with?

A

ret

66
Q

What are the clinical symptoms of NF1?

A

cafe au lait spots, optic pathway gliomas, lisch nodules, scoliosis, neural tumors

67
Q

what are lisch nodules?

A

pigmented iris hamartomas

68
Q

what are the clinical symptoms of NF2?

A

bilateral acoustic schwannomas, juvenile cataracts

69
Q

T/F the mode of inheritance for both NF disease is AR

A

false! Both AD!

70
Q

what is the inheritance of Tuberous Sclerosis?

A

AD

71
Q

What is the inheritance of Von Hippel Lindau disease?

A

AD

72
Q

what is the inheritance of CF? what is the pathogenesis of the disease?

A

AR; trinucleotide deletion results in loss of a Phe aa on CFTR gene on chrom 7- the result is a mutated CFTR channel that gets degraded in the ER before reaching the surface; the purpose of CFTR is to increase Cl secretion in luminal secretions and reabsorb Cl from sweat secretion

73
Q

T/F CFTR channel secretes Cl into sweat

A

False! reabsorbs Cl; secretes NaCl in luminal secretions

74
Q

What luminal secretions are affected in CF? What is wrong with the secretions?

A

respiratory, seminal fluid, pancreatic, gallbladder; very thick without NaCl to pull water

75
Q

What are the resp. clinical symptoms of CF?

A

thick mucus plugs lungs recurrent pulmonary infections (pseudomonas and aureus), chronic bronchitis, bronchiectasis (which can lead to cor pulmonale!); biofilms form on resp tract

76
Q

what are the GI clinical symptoms of CF?

A

chronic pancreatitis leads to type 1 diabetes, pancreatic insufficiency leads to ADEK deficiencies, malabsorption and steatorrhea, blocked gallbladder ducts leads to secondary biliary cirrhosis

77
Q

what systems are affected by CF?

A

pulmonary, GI, reproductive (infertility in male due to absence of vas deferens and seminal fluid thickness)

78
Q

what are two clinical symptoms of newborns with CF? and whats a lab value of a newborn with CF?

A

meconium ileus and failure to thrive; negative serum immunoreactive trypsin

79
Q

how is CF diagnosed?

A

increased concentration of Cl ions in sweat test

80
Q

How is CF treated? how does it work?

A

Nacetyl cysteine; breaks disulfide bridges of mucus plugs

81
Q

what is the mode of inheritance of the muscular dystrophies? what is the pathogenesis of the disease?

A

X linked recessive; deletion of the dystrophin gene (connects actin to the membrane glycoprotein) due to frame shift mutation- lack of dystrophin results in muscle breakdown which gets replaced by fibrofatty tissue and collagen

82
Q

what are the clinical symptoms of duchennes muscular dystrophy?

A

starts before age 5 with with pelvic girdle weakness with use of Gowers maneuver to stand up, it then progresses superiorly with muscle weakness (type 1 and 2!); waddling duck gait; hyporeflexia; pseudohypertrophy of calf muscles d/t fibrofatty replacement; cardiac myopathy

83
Q

how is muscular dystrophies diagnosed?

A

increased CPK and muscle biopsy

84
Q

what is the difference b/w beckers and duchennes muscular dystrophy?

A

beckers is less severe (instead of deletion is either defect or deficiency) with later presentation

85
Q

what is the pathogenesis of fragile x syndrome?

A

a trinucleotide repeat disorder results in faulty methylation and thus expression of the FMR1 gene on the X chromosome (x linked recessive mode of inheritance)

86
Q

what are the clinical symptoms associated with fragile X syndrome?

A

macroorchitism, big ears, big jaw, mental retardation (2nd mcc!), mitral valve prolapse, long face

87
Q

What are the four trinucleotide expansion disease and what are the expansions?

A

Myotonic Dystrophy (CTG), Huntington (CAG) Friedricks Ataxia (GAA), Fragile (CGG)

88
Q

what are the three mc autosomal trisomies in decreasing order?

A

Downs (21), Edwards (18), Pataus (13); also in increasing severity

89
Q

what is the mcc of an autosomal trisomy?

A

meiotic nondisjunction in mothers gametes during the first meiosis

90
Q

what are the clinical symptoms of Down syndrome?

A

mental retardation, flat faces, simean crease, epicanthal folds, ASD, duodenal atresia causing Hirshsprungs disease, redundant skin at the nape of neck, slanted palpebral fissures, hypotonia

91
Q

what is there on increased risk of with Downs?

A

ALL and Alzheimers

92
Q

what is the mc chromosomal disorder?

A

Downs

93
Q

what are the results of the pregnancy screen for Downs?

A

decrease AFP, increased BCHG, decreased estriol, increased inhibin A

94
Q

What does ultrasound show in Downs?

A

increased nuchal translucency

95
Q

what is the confirmation of Downs?

A

amniocentesis karyotyping

96
Q

what are the clinical findings in edwards syndrome?

A

mental retardation, rocker bottom feet, micrognathia (small jaw), low set ears, clenched hands with polydactyly, congenital heart disease

97
Q

what are the clinical findings in patau syndrome?

A

mental retardation, rocker bottom feet, micropthalmia, microcephaly, cleft lip/palate, holoprosoncephaly, polydactyly

98
Q

what is a robertsonian translocation? what does it mean if its balanced?

A

its when two acrocentric chromosomes combine their long arms (and short arms disappear); when the translocation is functional

99
Q

what is a common result of unbalanced robertsonian translocation?

A

chromosomal imbalance (downs for ex)

100
Q

what are the symptoms of cri du chat syndrome? what is the pathogenesis?

A

microcephaly, mental retardation, high pitched mewing/crying, epicanthal folds, cardiac abnormalities; microdeletion on short arm of chrom 5

101
Q

what are the symptoms of williams syndrome? what is the pathogenesis?

A

distinctive elfin faces, mental retardation, hypercalcemia d/t sensitivity to vit D, well developed verbal skills and extreme friendliness, CV problems

102
Q

What are the two 22q11 deletion syndromes? what is their pathogenesis? what is the difference between them?

A

DiGeorge and Velocardiofacial; deletion on chromosome 22q11 results in aberrant dev of 3rd and 4th branchial pouches; digeorge has thymic and parathyroid prob, velocardiofacial has palate and facial instead

103
Q

what are the general symptoms of 22q11 chromosomal deletion? why is it that these occur?

A

Cleft palate, Abnormal faces, thymic aplasia (t cell def), Cardiac defects, hypocalcemia (secondary to hypoparathyroid); 3rd and 4th branchial pouch aberrant development

USMLE1 - Biochemistry (6 decks)

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