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Pediatric Boards > Genetics > Flashcards

Genetics Flashcards

1
Q

What is variable expressivity?

A

when individuals have the same genetic condition (even the same genotype) but have varying degrees of the phentoype

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2
Q

What is mosaicism?

A

the presence of > 2 genetically different sets of cells in the same person caused by an error in mitosis

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3
Q

What does a quad screen check for, when is it done, and what genetic abnormalities does it screen for?

A
  • a-fetoprotein, hcg, estriol, inhibin A
  • between 15-18 weeks GA
  • measures likelihood of Trisomy 18, Trisomy 21, neural tube defects, abdominal wall defects
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4
Q

How do you prenatally screen from chromosomal disorders?

A

cell-free fetal DNA

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5
Q

What are ways to diagnose genetic disorders prenatally?

A
  • ultrasound
  • amniocentesis
  • chorionic villus sampling (placenta)
  • umbilical blood sampling
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6
Q

What factor is associated with increased risk of having baby w/ Trisomy 21?

A

increasing maternal age

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7
Q

What prenatal quad screen results are expected for Trisomy 21?

A
  • low maternal serum a-fetoprotein
  • low unconjugated estriol
  • elevated hcg
  • elevated inhibin

can also do early U/S screening fort nuchal translucency (neck thickness) to improve sensitivity/specificity of prenatal screening

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8
Q

Describe phenotypic presentation of Trisomy 21

A
  • hypotonia
  • poor Moro reflex
  • intellectual disability
  • brachydactyly (short, broad fingers and toes; big space between 1st/2nd toes)
  • upslanted palpebral fissures
  • flat midface
  • full cheeks
  • protruding tongue
  • epicanthial folds
  • single transverse palmar crease
  • Brushfield spots (whitish spots in ringlike configuration of iris)
  • high-arched palate
  • hypoplasia of middle phalanx of 5th finger
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9
Q

What medical issues can kids w/ Trisomy 21 have?

A
  • cardiac: AV canal defect, VSD, ASD
  • GI: duodenal atresia (double bubble sign), Hirschprung, celiac disease
  • ocular: cataracts
  • developmental: intellectual disability, early onset alzheimer/dementia
  • hypothyroidism
  • onc: leukemia (ALL), transient myeloproliferative disorder (typically self-resolves but increases risk of ALL development)
  • atlantoaxial (C1-C2) instability
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10
Q

Health Supervision Guidelines for Trisomy 21 patients

A
  • all routine immunizations
  • echocardiogram in newborn period
  • ophthalmologic eval before 6 mo old
  • hearing eval as newborn then again at 6 mo old
  • thyroid studies at newborn, 6 mo, 12 mo then annually
  • vision screening at 4 yo
  • only do cervical spine imaging if symptomatic w/ signs of myelopathy
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11
Q

What are features of someone with Trisomy 18 (Edwards Syndrome)?

A
  • IUGR
  • intellectual disability
  • high forehead
  • microcephaly
  • small face/mouth
  • rocker bottom feet
  • overlapping fingers
  • short sternum
  • hypoplastic nails
  • structural cardiac defects

Most die in first week or within first year.

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12
Q

What are features of someone with Trisomy 13 (Patau Syndrome)?

A

Midline deficiency

  • orofacial cleft (midline cleft lip)
  • microphthalmia
  • low-set dysplastic ears
  • spinal cord abnormalities
  • postaxial (aka ulnar) polydactyly of limbs
  • holoprosencephaly
  • heart malformations
  • hypoplastic or absent ribs
  • genital anomalies
  • abdominal wall defects
  • aplasia cutis congenita (absence of layer of skin)
  • rocker bottom feet
  • clenched hands
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13
Q

What are the Sex Chromosome Syndromes?

A
  • 47XXY Klinefelter
  • 47 XYY
  • 47 XXX
  • 45 X Turner
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14
Q

What are the clinical features of Turner Syndrome?

A

45, X

  • short stature w/ ovarian failure/gonadal dysgenesis w/ lack of 2/2 sex characteristics
  • cardiac anomalies - bicuspid aortic valves, coarcted aorta
  • renal anomalies - horseshoe kidney, duplicate collecting system, abnormal vasculature
  • hearing loss (can be progressive sensorineural)
  • at birth: broad webbed neck, shield-like chest, posteriorly rotated ears, lymphedema of hands/feet, short 4th metacarpals, cubitus valgus
  • childhood/adulthood: chronic AI thyroiditis (hashimoto), alopecia, carb intolerance, vitiligo, GI disorders (ex celiac)
  • if have some Y material - ⇡ risk for gonadoblastoma (need to be removed)
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15
Q

What are the clinical features of Klinefelter Syndrome?

A

47, XXY

  • male phenotype
  • tall
  • gynecomastia
  • delayed 2/2 sex characteristic development
  • azoospermia and small testes → infertile
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16
Q

What are the clinical features of someone born 47, XYY?

A
  • not a true syndrome
  • taller than average
  • severe nodular-cystic acne
  • commonly have developmental delay and behavioral problems
  • prolonged PR interval
17
Q

How are microdeletion syndromes diagnosed?

A
  • too small to detect via karyotype
  • fluorescence in situ hybridization (FISH) - looks at specific pre-defined region
  • chromosomal microarray (aka comparative genomic hybridization)
  • oligonucleotide microarray and SNP array - can find small areas of deletion
18
Q

What are clinical features of Williams Syndrome (7q11.23 deletion)?

A
  • broad forehead, medial eyebrow flare, short upturned nose w/ flattened nasal bridge, elongated philtrum w/ downturned lower lip (elfin facies)
  • friendly personality
  • stellate pattern of iris
  • strabismus
  • supravalvular aortic stenosis
  • intellectual disability
  • hypersensitivity to loud sounds
  • hypercalcemia
  • connective tissue anomalies (lax joints, soft skin)
  • growth delay and short stature
  • perioorbital fullness
19
Q

What are the clinical features of WAGR syndrome (11p13 deletion)?

A
  • Wilms tumor - in 50% of cases
  • Aniridia - no iris
  • GU abnormalities - male genital hypoplasia (hypospadias, cryptorchidism, small penis, and/or hypoplastic scrotum)
  • Reduced intellectual abilities - from low IQ to nml
  • gonadoblastoma
  • long face
  • upward-slanting palpebral fissures
  • ptosis
  • beaked nose
  • poorly formed ears
20
Q

What are the clinical features of Alagille Syndrome (20p12 deletion)?

A
  • AD inheritance
  • triangular facies w/ pointed chin
  • long nose w/ broad midnose
  • bile duct paucity w/ cholestasis
  • pulm valve stenosis and peripheral valve stenosis
  • ocular defects
  • skeletal defects (butterfly vertebrae)
21
Q

What are the clinical characteristics of DiGeorge Syndrome (22q11.2)?

A

CATCH-22

Developm

  • Cardiac defects - ToF > interrupted aortic arch > VSD > truncus arteriosus
  • Abnormal facies - tubular nose, hooded eyelids, small chin, small ears
  • Thymic hypoplasia
  • Cleft defects
  • Hypocalcemia - due to parathyroid gland agenesis or hypoplasia
  • Chromosome 22
  • short stature
  • behavioral problems

Pediatric Boards (5 decks)

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