Trisomies/monsomies

Question 1

Downs

Answer 1

• trisomy 21
• 1:700
• reduced maternal levels of alpha foetoprotein, increased beta HCG and increased nuchal fold thickness in fetal ultrasound
• child has mental retardation, flat facial profile, prominent epicanthal folds, simian crease, duodenal atresia, hypothyroidism and heart disease
• Alzheimers and leukaemia are common
• 95% is due to meiotic non-disjunction of homologous chromosomes associated with advanced maternal age
• 4% due to robertson translocation
• 1% due to mosacism

Question 2

Edwards syndrome

Answer 2

• trisomy 18
• severe mental retardation and rocker btotom feet, low set ears, micrognathia, congenital heat disease, clenched hands and prominent occuput
• 1:8000
• death occurs within 1 year of birth
• 3x more common in girls than boys

Question 3

Patau’s syndrome

Answer 3

• due to trisomy 13
• characterised by severe mental retardation, microphthalmia, microcephal, cleft lip/palate, coloboma eye, abnormal forebrain structures, polydactyly, congenital heart disease

Question 4

Metafemale

Answer 4

-trisomy X

Question 5

Turner’s syndrome

Answer 5

• 45X
• low hairline, broad chest, short stature, retrognathism and webbed neck
• 1/2000
• IQ can be a bit lower, bettrer verbal skills if the X chromosome is male derived