Genetics Flashcards
What is the inheritance pattern of familial hypercholesterolaemia?
autosomal dominant
What criteria is used to diagnose familial hypercholesterolaemia?
Simon-Broome criteria - definite or possible FH
What are the Simon-Broome criteria for definite familial hypercholesterolaemia?
Total cholesterol >7.5 + LDL >4.9 + tendon xanthomata in patient OR in first or second degree relative
OR
identified genetic mutation for FH
What are the Simon-Broome criteria for possible familial hypercholesterolaemia?
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
What is the commonest cardiac defect in Down syndrome and what are 4 others?
AVSD (VSD, ASD, PDA, Tetralogy of Fallot)
What is the equation to calculate the risk of giving birth to a baby with Downs based on mother’s age?
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)
What are the 3 genetic mechanisms that can lead to Down syndrome and their relative frequencies?
- Non-disjunction - 94%
- Robertsonian translocation (onto chromosome 14 usually) - 5%
- Mosaicism - 1%
If a mother is <35y, what is the chance of a second child with Downs?
1 in 100 (higher if due to translocation)
What are 5 features of Patau syndrome?
- Microcephalic
- small eyes
- cleft lip / palate
- polydactyly
- scalp lesions
What is the genetic abnormality in Patau syndrome?
Trisomy 13
What is the genetic abnormality in Edward’s syndrome?
trisomy 18
What are 4 features of Edward’s syndrome?
- micrognathia
- low-set ears
- Rocker-bottom feet
- overlapping of fingers
What are 5 features of fragile X syndrome?
- learning difficulties
- macrocephaly
- long face
- large ears
- macro-orchidism
What are 4 features of Noonan syndrome?
- Webbed neck
- Pectus excavatum
- Short stature
- Pulmonary stenosis
What are 3 features of Pierre-Robin syndrome?
- Micrognathia
- Posteiror displacement of tongue (may cause upper airway obstruction)
- Cleft palate
What are 3 features of Prader-Willi syndrome?
- Hypotonia
- Hpogonadism
- Obesity
What are 5 features of William’s syndrome?
- Short stature
- Learning difficulties
- Friendly, extrovert personality
- Transient neonatal hypercalcaemia
- Supravalvular aortic stenosis
What are 6 features of Cri du Chat syndrome?
- Characteristic cry due to larynx / neuro problems
- Feeding difficulties, poor weight gain
- Learning difficulties
- Microcephaly
- Micrognathism
- Hypertelorism (increased distance between 2 body parts)
Which condition does Pierre-Robin syndrome resemble?
Treacher-Collins syndrome - this is autosomal dominant so FH prevalent
What is the genetic abnormality in Cri du Chat syndrome?
chromosome 5p deletion syndrome
What is the inheritance pattern of dystrophinopathies (Duchenne muscular dystrophy and Becker muscular dystrophy)?
X-linked recessive
What causes dystrophinopathies?
- 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)
What causes Duchenne muscular dystrophy?
frameshift mutation resulting in one or both binding sites being lost, leading to severe form
What is the inheritance pattern of familial hypercholesterolaemia?
autosomal dominant