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a Paediatrics by themes > Genetics > Flashcards

Genetics Flashcards

1
Q

What chromosomal abnormality causes Patau’s syndrome?

A

Trisomy 13

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2
Q

What are the features of Patau’s syndrome?

A
  • Cardiac defects = VSD, PDA, dextrocardia
  • Microcephaly and brain defects
  • Microphthalmia (small eyes)
  • Other eye defects
  • Cleft lip/palate
  • Polydactyl
  • Omphalocele / Gastroschisis (abdominal wall defects)
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3
Q

What chromosomal abnormality causes Edward’s syndrome?

A

Trisomy 18

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4
Q

What are the features of Edward’s syndrome?

A
  • LBW
  • Small mouth/chin
  • Low-set ears
  • ‘Rocker-bottom’ feet
  • Overlapping fingers
  • Intellectual disability
  • Cardiac, renal and GI abnormalities
  • Omphalocele / Gastroschisis (abdominal wall defects)
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5
Q

What chromosomal abnormality causes Down’s syndrome?

A

Trisomy 21

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6
Q

What are the features of Down’s syndrome?

A
  • Characteristic facies
  • Hypotonia and short neck
  • Single palmar crease
  • ‘Sandal gap’ on feet
  • Short stature
  • Upslanting palpebral fissures
  • Flat occiput
  • Congenital heart defects in 40%
  • Omphalocele / Gastroschisis (abdominal wall defects)
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7
Q

What genetic abnormality causes Noonan’s syndrome?

A

Mutated RAS/Mitogen Activated Protein Kinase

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8
Q

What are the features of Down’s syndrome?

A
  • Webbed neck
  • Trident hairline
  • Pectus excavatum
  • Short stature
  • Pulmonary stenosis
  • Low IQ - most common cause
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9
Q

What genetic abnormality causes Prader-Willi syndrome?

A

Lacks paternal 15q

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10
Q

What genetic abnormality causes Angelman’s syndrome?

A

Lacks maternal 15q

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11
Q

What are the features of Prader-Willi syndrome?

A
  • Hypotonia
  • Hyperphagia
  • Almond-shaped eyes
    • Fat, floppy, flaccid
  • Hypogonadism
  • Obesity (in later childhood)
  • Epicanthal folds
  • Flat nasal bridge + upturned nose
  • Learning disability
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12
Q

What are the features of Angelman syndrome?

A
  • Cognitive impairment
  • Ataxia
  • Epilepsy
  • Abnormal facial appearance
  • Myoclonic seizures
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13
Q

What chromosomal abnormality causes Turner’s syndrome?

A

45 X

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14
Q

What are the features of Turner’s syndrome?

A
  • Lymphoedema of hands/feet in neonate
  • Short stature, spoon-shaped nails
  • Wide carrying angle
  • Thick or webbed neck
  • Infertility
  • Bicuspid aortic valve > Aortic coarctation
    • ESM over aortic valve
  • Delayed puberty / Infertility
  • Hypothyroidism
  • Omphalocele / Gastroschisis (abdominal wall defects)
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15
Q

What chromosomal abnormality causes Klinefelter’s syndrome?

A

47 XXY

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16
Q

What are the features of Klinefelter’s syndrome?

A
  • Infertility
  • Hypogonadism (small testicles)
  • Gynaecomastia
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17
Q

What genetic abnormality causes Fragile X syndrome?

A

CGG trinucleotide repeat expansion mutation (fragile) to the FMR1 gene

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18
Q

What are the features of Fragile X syndrome?

A
  • IQ 20-80 (mean 50) – 2nd most common cause of low IQ after Down’s Syndrome
  • Macrocephaly
  • Macroorchidism
  • Characteristic facies
    • Large, low-set ears
    • Long, thin face
  • Other – autism, joint laxity, scoliosis
  • Mitral valve prolapse - common complication
19
Q

Define Malformation.

A

Primary structural defect occurring during the development of a tissue/organ.

20
Q

Define Defomration.

A

Abnormal intrauterine mechanical force that distorts a normally formed structure (e.g. oligohydramnios).

21
Q

Define Disruption.

A

Destruction of a foetal part that may have initially formed normally.

22
Q

Define Dysplasia.

A

Abnormal cellular organisation or function.

23
Q

Define Single System Defect.

A

Single congenital malformations.

24
Q

Define Sequence.

A

Pattern of multiple abnormalities occurring after one initiating defect - i.e. posterior urethral valves.

25
Q

Define Association.

A

Group of malformations that occur together but in different combinations case to case.

26
Q

Define Syndrome.

A

Multiple abnormalities occurring repeatedly in a consistent pattern, common underlying causal mechanism.

27
Q

What are the signs and symptoms of foetal alcohol syndrome?

A
  • Microcephaly
  • Absent philtrum
  • Cardiac abnormalities
  • Reduced IQ
  • IUGR
  • Small upper lip
28
Q

What are the signs and symptoms of cigarette smoking in pregnancy?

A
  • IUGR
  • Miscarriage
  • Stillbirth
29
Q

What are the signs and symptoms of syphilis infection in a neonate?

A
  • Rhinitis
  • Saddle-nose
  • Deafness (sensorineural)
  • Hepatosplenomegaly
  • Jaundice
30
Q

What is the prognosis of Patau’s syndrome?

A
  • 80% die in first month of life
  • 90% by 1 year of age
31
Q

What are the appropriate investigations for suspected Patau’s syndrome?

A
  • USS analysis in 2nd trimester
  • Chromosomal analysis from amniocentesis/cffDNA
32
Q

What is the prognosis of Edward’s syndrome?

A

Many will die in infancy → prolonged survival is possible

33
Q

What are the appropriate investigations for suspected Edward’s syndrome?

A
  • USS analysis in 2nd trimester
  • Chromosomal analysis from amniocentesis/cffDNA
34
Q

What is the prognosis of Noonan’s syndrome?

A
  • Penetrance varies greatly
    • From lethal prenatally to minimal morbidity
35
Q

What is the management of Prader-Willi syndrome?

A
  • Growth hormone if clinical evidence of growth failure
  • Management of feeding and obesity (i.e. lock cupboards)
36
Q

What are the signs and symptoms of neonatal Turner’s syndrome?

A
  • Pyloric stenosis
  • Cardiac problems
    • Coarctation of aorta
    • Bicuspid aortic valve
    • AS murmur = ESM over aortic valve
  • Renal anomalies
  • Cystic hygroma - may resolve early → skin on the back of the neck
37
Q

Name 3 trinucleotide repeat-expansion mutations.

A
  • Fragile X syndrome
  • Myotonic dystrophy
  • Huntington disease
38
Q

What is the chromosomal pathogenesis of Down’s syndrome?

A
  • Meiotic non-disjunction - linked to maternal age
    • Error at meiosis, pair of chromosomes 21 fail to separate (one gamete has 2 x 21 and one has none)
    • 94%
    • No need to examine parental chromosome
  • Translocation
    • Extra chromosome 21 is joined to another chromosome (usually 14)
    • Robertsonian translocation
    • 5%
    • Parental Chr analysis is recommended
    • Risk of recurrence 10-15% if mother is translocation carrier
  • Mosaicism
    • Milder phenotype, some cells are normal, and some have trisomy 21, formation of chromosomally normal zygote but non-disjunction at mitosis
    • 1%
39
Q

What are the craniofacial signs of Down’s syndrome?

A
  • Round face
  • Flat nasal bridge
  • Epicanthic folds
  • Brushfield spots in iris
  • Small mouth
  • Small ears
  • Flat occiput
  • 3rd fontanelle
  • Short neck
  • Single palmar crease
  • Sandal-gap
  • Hypotonia
40
Q

What are the medical problem present at birth in Down’s syndrome?

A
  • Congenital heart defects - 40%
  • Duodenal atresia
  • Hirschprung’s disease
  • Omphalocele ± umbilical hernia
41
Q

What are the medical problem present later if life in Down’s syndrome?

A
  • Delayed motor milestones
  • Learning difficulty / Low IQ
  • Short stature
  • Secretory otitis media (75%)
  • Visual impairment (25-50%)
  • OSA (50-75%)
  • Increased disease chance:
    • Leukaemia (not ALL)
    • Hypothyroidism
    • Coeliac’s
    • Epilepsy
    • Early-onset Alzheimer’s
  • Joint laxity - screen for atlantoaxial instability in those doing sports → risk of neck dislocation
42
Q

What congenital conditions are associated with Down’s syndrome?

A
  • Kostmann’s syndrome
  • Bloom syndrome
  • Fanconi syndrome / Diamond-Blackfan
  • NF1
  • Li Fraumeni syndrome
43
Q

What is the management of Down’s syndrome at birth?

A
  • Echocardiogram - AVSD
  • Evaluation by paediatricians - duodenal atresia
  • Genetic counselling
  • Early intervention programmes if developmental delay is present
    • Physiotherapy → prevent abnormal compensatory movements for physical limitations
    • OT → fine motor and self-care
    • SALT → speech intelligibility and to manage language delay
44
Q

What is the management of Down’s syndrome in children?

A
  • Annual tests
    • Hearing test
    • Thyroid levels
    • Ophthalmic evaluation (up to 5 years then every 2 years)
  • Appropriate education with an individualised educational plan
  • Haemoglobin level for IDA
  • Monitor for symptoms of sleep apnoea
  • Monitor growth using updated Down’s syndrome growth charts

a Paediatrics by themes (26 decks)

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