Chromosome Syndromes
Down Syndrome:
Most
common chromosomal syndrome
95%
are due to trisomy 21 (an extra 21 chromosome)
Risk
increases with age of mother:
At age 30 – 1/900
births
At age 40 – 1/100
births
Trisomy 13
Syndrome:
Forebrain
malformation, severe growth & mental retardation
Trisomy 18
Syndrome:
Mental
retardation, microcephaly, rocker-bottom feet