Genetics Flashcards
Clinical features T21 (at birth)
Facies Hypotonic Flat occiput Single palmar crease Incurved 5th finger Sandal gap
Ix T21
FISH
Congenital heart disease prevalence in T21
30%
50 year survivial T21
50%
Commonest cause of T21
Meiotic nondisjunction
Incidence T21
1/650
Incidence T18
1/8000
Incidence T13
1/14000
Immediate medical complications T21
Congenital heart disease - AVSD
Duodenal atresia
Incidence Turner’s
1/2500 live births (95% result in miscarriage)
Antenatal USS findings Turner’s
Fetal oedema of neck, hands, feet
Cystic hygroma
Neonatal features Turner’s
Lymphoedema hands and feet Spoon nails Short stature Neck webbing Widely spaced nipples
Mx Turner’s
GH therapy Oestrogen replacement (secondary sex characteristics - infertility persists)
Di George genetic abnormality
Deletion band q11 on chr22
Commonest mode of mendelian inheritance
AD
Examples AD inheritance
Achondroplasia Marfan Huntington Marfan Myotonic dystrophy Noonan Osteogenesis imperfecta Tuberous sclerosis
Examples AR inheritance
Congenital adrenal hyperplasia Cystic fibrosis Galactosaemia PKU SCD Thalassaemia
What do AD disorders often affect?
Structural proteins
What do AR disorders often affect?
Metabolic pathways
Examples XR inheritance
Muscular dystrophies
Haemophilias
Fragile X
G6PD deficiency
Trinucleotide repeat expansion mutations examples
Fragile X
Huntingtons
Deletion affecting bands 11-13 on Chr 15 (MATERNAL/PATERNAL)
Maternal deletion - Angelman
Paternal deletion - Prader-Willi
Prader-Willi features
Hpotonia Hyperphagia Developmental delay Obesity Hypogonadism