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UWorld Review > Genetics > Flashcards

Genetics Flashcards

1
Q

Duchenne dystrophy characteristics

A
  • X-linked
  • Frameshift deletion/nonsense
  • truncated/absent dystrophin protein = progressive myofiber damage
  • increase CK and aldolase
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2
Q

What is the largest protein-coding human gene

A

Dystrophin gene (DMD)

  • increase chance of spontaneous mutation
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3
Q

What does dystophin do

A
  • helps anchor muscle fibers in skeletal/cardiac muscle
  • connects intracellular cytoskeleton (actin) to transmembrane proteins alpha/beta-dystroglycan - which are connected to ECM
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4
Q

Loss of dystrophin causes

A

myonecrosis

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5
Q

Gowers sign can be seen in

A
  • Duchenne (classic)
  • other muscular dystrophy
  • inflammatory dystrophy (polymyositis)
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6
Q

Duchenne weakness begins where

A

pelvic girdle muscles and progresses superiorly

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7
Q

Becker muscular dystrophy characteristics

A
  • X-linked
  • non-frameshift deletions in dystrophin gene
  • gene partially functional, not truncated
  • less severe than Duchenne
  • adolescent/early adult onset
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8
Q

Deletions in dystrophin gene can cause what two dystrophies

A

Duchenne

Becker

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9
Q

Characteristics of myotonic type 1 dystrophy

A
  • AD
  • CTG trinucleotide repeat expansion in DMPK gene
  • abnormal expression of myotonin protein kinase
  • myotonia (difficulty releasing from handshake)
  • muscle wasting
  • cataracts
  • testicular atrophy
  • frontal balding
  • arrythmia
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10
Q
  • Cataracts
  • early balding in men
  • gonadal atrophy
  • can’t release from handshake
A

Myotonic type 1 dystrophy

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11
Q

Characteristics of Rett syndrome

A
  • almost always girls
  • sporadic disorder
  • MCC de novo mutation MECP2 on X chr
  • onset 1-4 yrs
  • regression in motor, verbal, cognitive abilities
  • ataxia
  • seizures
  • growth failure
  • hand-wringing
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12
Q

What happens to males with Rett syndrome

A

die in utero or shortly after birth

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13
Q
  1. CGG trinucleotide repeat
  2. XD
  3. long face w/protruding chin
  4. post-pubertal giant gonads
  5. large elevated ears
  6. MVP
A

Fragile X syndrome

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14
Q

Fragile X syndrome caused by

A

CGG trinucleotide repeat in FMR1 gene

  • hypermethylation = decreased expression
  • LOF mutation
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15
Q

MCC of inherited intellectual disability

2nd MCC of genetically associated mental deficiency

A

Fragile X syndrome

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16
Q

What does trinucleotide repeat expansion occur in Fragile X syndrome

A

oogenesis

17
Q

What happens to girls with fragile X syndrome

A

less severe disease

18
Q
  • CAG trinucelotide repeat
  • AD
  • caudate has decreased Ach and GABA
A

Huntington disease

19
Q
  • CTG trinucleotide repeat
  • AD
  • cataracts
  • early balding in men
  • gonadal atrophy
  • myotonia
A

Myotonic dystrophy

20
Q
  • AR
  • GAA trinucelotide repeat
  • ataxic gait
A

Friedreich ataxia

21
Q

What are the 5 A’s of Down syndrome

A
  1. Advanced maternal age
  2. Atresia (duodenal)
  3. Atrioventricular septal defect
  4. Alzheimer disease (early onset)
  5. AML/ALL
22
Q

GI manifestations of Downs syndrome

A

duodenal atresia

Hirschsprung disease

23
Q

First trimester test for Down syndrome

A
  • increased nuchal translucency
  • hypoplastic nasal bone
  • increased hCG and inhibin
24
Q

Down syndrome lab in second trimester

A

increased hCG and inhibin A

decreased estriol and AFP

25
Q

First trimester labs for Edwards and Patau

A

decreased hCG and PAPP-A

26
Q

2nd trimester lab for Edward syndrome

A

hCG, inhibin A, estriol, AFP all decreased

(inhibin A might be normal)

27
Q

Gi manifestation of Edwards syndrome

A

Meckel/malrotation

omphalocele

small jaw (micrognathia)

28
Q

heart manifestation of Edwards syndrome

A

VSD, PDA

29
Q

Edwards syndrome is d/t

A

meiotic nondisjunction

  • error in oocyte division
  • prior to ovulation and fertilization
30
Q

What is seen on U/S for Edwards syndrome

A

fetal growth restriction

31
Q

Congenital deletion of short arm of chr 5

46 XX or XY, 5p-

A

Cri-du-chat syndrome

32
Q

Characteristics of cri-du-chat syndrome

A
  • microcephaly
  • moderate to severe intellectual disability
  • high pitched cry/meowing
  • epicanthal folds
  • cardiac abnormalities (VSD)
33
Q

Congenital microdeletion of long arm of chr 7

A

Williams syndrome

34
Q
  • Elfin facies
  • intellectual disability
  • hypercalcemia
  • well-developed verbal skills
  • extreme friendliness w/strangers
  • cardiovascular problems
  • renal artery stenosis
A

Williams syndrome

35
Q

What cardiac problems seen in Williams syndrome

A
  1. supravalvular aortic stenosis
  2. renal artery stenosis
36
Q

what 3 genetic disorders are associated with X chromosome

A
  1. Fragile X syndrome
  2. X-linked agammablogulinemia
  3. Klinefelter syndrome
37
Q

What chromosome are NF1, BRCA1, and TP53 associated with

A

chromsome 17

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