Genetics Flashcards
What chromosomal abnormality causes Patau’s syndrome?
Trisomy 13
What are the features of Patau’s syndrome?
- Cardiac defects = VSD, PDA, dextrocardia
- Microcephaly and brain defects
- Microphthalmia (small eyes)
- Other eye defects
- Cleft lip/palate
- Polydactyl
- Omphalocele / Gastroschisis (abdominal wall defects)
What chromosomal abnormality causes Edward’s syndrome?
Trisomy 18
What are the features of Edward’s syndrome?
- LBW
- Small mouth/chin
- Low-set ears
- ‘Rocker-bottom’ feet
- Overlapping fingers
- Intellectual disability
- Cardiac, renal and GI abnormalities
- Omphalocele / Gastroschisis (abdominal wall defects)
What chromosomal abnormality causes Down’s syndrome?
Trisomy 21
What are the features of Down’s syndrome?
- 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)
What genetic abnormality causes Noonan’s syndrome?
Mutated RAS/Mitogen Activated Protein Kinase
What are the features of Down’s syndrome?
- Webbed neck
- Trident hairline
- Pectus excavatum
- Short stature
- Pulmonary stenosis
- Low IQ - most common cause
What genetic abnormality causes Prader-Willi syndrome?
Lacks paternal 15q
What genetic abnormality causes Angelman’s syndrome?
Lacks maternal 15q
What are the features of Prader-Willi syndrome?
- Hypotonia
- Hyperphagia
- Almond-shaped eyes
- Fat, floppy, flaccid
- Hypogonadism
- Obesity (in later childhood)
- Epicanthal folds
- Flat nasal bridge + upturned nose
- Learning disability
What are the features of Angelman syndrome?
- Cognitive impairment
- Ataxia
- Epilepsy
- Abnormal facial appearance
- Myoclonic seizures
What chromosomal abnormality causes Turner’s syndrome?
45 X
What are the features of Turner’s syndrome?
- 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)
What chromosomal abnormality causes Klinefelter’s syndrome?
47 XXY
What are the features of Klinefelter’s syndrome?
- Infertility
- Hypogonadism (small testicles)
- Gynaecomastia
What genetic abnormality causes Fragile X syndrome?
CGG trinucleotide repeat expansion mutation (fragile) to the FMR1 gene
What are the features of Fragile X syndrome?
- 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
Define Malformation.
Primary structural defect occurring during the development of a tissue/organ.
Define Defomration.
Abnormal intrauterine mechanical force that distorts a normally formed structure (e.g. oligohydramnios).
Define Disruption.
Destruction of a foetal part that may have initially formed normally.
Define Dysplasia.
Abnormal cellular organisation or function.
Define Single System Defect.
Single congenital malformations.
Define Sequence.
Pattern of multiple abnormalities occurring after one initiating defect - i.e. posterior urethral valves.