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DrFeelGood Stuffs > Genetics > Flashcards

Genetics Flashcards

1
Q

What is the inheritance pattern of familial hypercholesterolaemia?

A

autosomal dominant

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2
Q

What criteria is used to diagnose familial hypercholesterolaemia?

A

Simon-Broome criteria - definite or possible FH

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3
Q

What are the Simon-Broome criteria for definite familial hypercholesterolaemia?

A

Total cholesterol >7.5 + LDL >4.9 + tendon xanthomata in patient OR in first or second degree relative
OR
identified genetic mutation for FH

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4
Q

What are the Simon-Broome criteria for possible familial hypercholesterolaemia?

A

Total cholesterol >7.5 + LDL >4.9 + 1 or more of the following:
* FH early MI <60y in 1st degree relative or <50y in 2nd degree relatie
* FH raised TC - >7.5 in first or second degree adult relative or >6.7 in brother, sister or child <16y

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5
Q

What is the commonest cardiac defect in Down syndrome and what are 4 others?

A

AVSD (VSD, ASD, PDA, Tetralogy of Fallot)

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6
Q

What is the equation to calculate the risk of giving birth to a baby with Downs based on mother’s age?

A

risk = 1/1000 at 30 years, then divide by 3 for every 5 years beyond 30 (e.g. 45 years old - 1 in 50 or greater)

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7
Q

What are the 3 genetic mechanisms that can lead to Down syndrome and their relative frequencies?

A
  • Non-disjunction - 94%
  • Robertsonian translocation (onto chromosome 14 usually) - 5%
  • Mosaicism - 1%
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8
Q

If a mother is <35y, what is the chance of a second child with Downs?

A

1 in 100 (higher if due to translocation)

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9
Q

What are 5 features of Patau syndrome?

A
  1. Microcephalic
  2. small eyes
  3. cleft lip / palate
  4. polydactyly
  5. scalp lesions
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10
Q

What is the genetic abnormality in Patau syndrome?

A

Trisomy 13

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11
Q

What is the genetic abnormality in Edward’s syndrome?

A

trisomy 18

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12
Q

What are 4 features of Edward’s syndrome?

A
  1. micrognathia
  2. low-set ears
  3. Rocker-bottom feet
  4. overlapping of fingers
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13
Q

What are 5 features of fragile X syndrome?

A
  1. learning difficulties
  2. macrocephaly
  3. long face
  4. large ears
  5. macro-orchidism
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14
Q

What are 4 features of Noonan syndrome?

A
  1. Webbed neck
  2. Pectus excavatum
  3. Short stature
  4. Pulmonary stenosis
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15
Q

What are 3 features of Pierre-Robin syndrome?

A
  1. Micrognathia
  2. Posteiror displacement of tongue (may cause upper airway obstruction)
  3. Cleft palate
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16
Q

What are 3 features of Prader-Willi syndrome?

A
  1. Hypotonia
  2. Hpogonadism
  3. Obesity
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17
Q

What are 5 features of William’s syndrome?

A
  1. Short stature
  2. Learning difficulties
  3. Friendly, extrovert personality
  4. Transient neonatal hypercalcaemia
  5. Supravalvular aortic stenosis
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18
Q

What are 6 features of Cri du Chat syndrome?

A
  1. Characteristic cry due to larynx / neuro problems
  2. Feeding difficulties, poor weight gain
  3. Learning difficulties
  4. Microcephaly
  5. Micrognathism
  6. Hypertelorism (increased distance between 2 body parts)
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19
Q

Which condition does Pierre-Robin syndrome resemble?

A

Treacher-Collins syndrome - this is autosomal dominant so FH prevalent

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20
Q

What is the genetic abnormality in Cri du Chat syndrome?

A

chromosome 5p deletion syndrome

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21
Q

What is the inheritance pattern of dystrophinopathies (Duchenne muscular dystrophy and Becker muscular dystrophy)?

A

X-linked recessive

22
Q

What causes dystrophinopathies?

A
  • mutation in gene encoding dystrophin, dystrophin gene on Xp21
  • dystrophin is part of large membrane associated protein in muscle which connects muscle membrane to actin (part of muscle cytoskeleton)
23
Q

What causes Duchenne muscular dystrophy?

A

frameshift mutation resulting in one or both binding sites being lost, leading to severe form

24
Q

What is the inheritance pattern of familial hypercholesterolaemia?

A

autosomal dominant

25
Q

What causes Becker muscular dystrophy?

A

non-frameshift insertion in dustrophin gene - results in both binding sites being preserved

26
Q

What is the presentation of Duchenne muscular dystrophy? 4 features

A
  1. progressive proximal muscle weakness from age 5
  2. calf pseudohypertrophy
  3. Gower’s sign (using arms to stand from squatting)
  4. intellectual impairment 30%
27
Q

What age does Becker muscular dystrophy tend to develop?

A

after age 10

28
Q

How common is intellectual impairment in Duchenne vs. Becker muscular dystrophy?

A

much less common in Becker

29
Q

What type of cholesterol is high in familial hypercholesterolaemia?

A

LDL

30
Q

What 2 criteria do NICE suggest should suggest familial hypercholesterolaemia in adults?

A
  1. total cholesterol > 7.5
  2. personal or FH premature coronary heart disease (< 60 years)
31
Q

How should children of parents with familial hypercholesterolaemia be managed?

A
  1. one parent with familial hypercholesterolaemia - arrange testing by age 10
  2. if both parents - arrange testing in age 5
32
Q

What is the name of the criteria which allows a clinical diagnosis of familial hypercholesterolaemia?

A

Simon Broome Criteria

33
Q

What are the 3 groups of Simon Broome criteria for familial hypercholesterolaemia?

A
  1. Adults: total cholesterol > 7.5 and LDL > 4.9; children TC > 6.7, LDL > 4.0 PLUS
  2. definite diagnosis: tendon xanthmoa in patients or 1st or 2nd degree relatives, or DNA-based evidence
  3. possible diagnosis: FH of MI < 50 y in 2nd degree relative, < 60 y in first degree relative, FH raised cholesterol
34
Q

What is the management of familial hypercholesterolaemia?

A
  • refer to specialist lipid clinic
  • high dose statins
  • screen first degree relatives
35
Q

When should statins be discontinued in women with familial hypercholesterolaemia and why?

A

3 months before conception - risk of congenital defects

36
Q

What are 7 key features of Turner’s syndrome?

A
  1. short stature
  2. shield chest, widely spaced nipples
  3. webbed neck
  4. cardiac: bicuspid aortic valve + coarctation of aorta
  5. primary amenorrhoea
  6. high-arched palate
  7. short ring fingers (short fourth metacarpal)
37
Q

What are 4 classic cardiac abnormalities in Turner’s syndrome?

A
  1. bicuspid aortic valve
  2. coarctation of the aorta
  3. increased risk of aortic dilatation
  4. increased risk of aortic disscetion
38
Q

What is the most common renal abnormality in Turner’s syndrome?

A

horseshoe kidney

39
Q

What is a key blood test finding in Turner’s syndrome?

A

elevated gonadotrophin levels

40
Q

Which type of genetic abnormalities are particularly prone to demosntrating anticipation?

A

trinucleotide repeat disorders

41
Q

What are 7 examples of trinucleotide repeat disorders (prone to anticipation)?

A
  1. Fragile X
  2. Huntington’s
  3. myotonic dystrophy
  4. Friedrich’s ataxia
  5. spinocerebellar ataxia
  6. spinobulbar muscular atrophy
  7. dentatorubral pallidoluysian atrophy
42
Q

What is the commonest cardiac problem in Down’s syndrome?

A

endocardial cushion defect (aka atroventricular septal canal defects)

43
Q

What are 2 GI problems which may be seen in Down syndrome?

A
  1. duodenal atresia
  2. Hirschprung disease
44
Q

How does subfertility in Down syndrome occur in males vs females?

A
  • males: almost always infertile (impaired spermatogenesis)
  • females: usually subfertile, increased incidence of problems with pregnancy and labour
45
Q

What is the commonest type of cancer seen in Down syndrome?

A

acute lymphoblastic leukaemia

46
Q

What MSK is seen as a later complication in Down syndrome?

A

atlantoaxial instability

47
Q

Which chromosome is the genetic abnormality in Huntington’s disease on?

A

chromosome 4 (huntingtin gene)

48
Q

What is the commonest inherited autosomal recessaive ataxia in the UK?

A

Friedrich’s ataxia

49
Q

What are patients with Friedrich’s ataxia most likely to die from?

A

cardiomyopathy

50
Q

What are 5 presenting symptoms of Friedrich’s ataxia?

A
  1. unsteadiness of gait
  2. general clumsiness or deterioration in athletic performance
  3. scoliosis
  4. pes cavus
  5. progressive ataxia, dysarthria, decreased proprioception/vibration sense and muscle weakness

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