Which of the following is FALSE of Down syndrome?
◦ Studying individuals with partial trisomy of chromosome 21 identified the Down syndrome critical region (DSCR) with a small number of genes responsible for the principal symptoms.
◦ There are homologs in model organisms, such as mice and Drosophila, for genes in the Down syndrome critical region (DSCR).
◦ Molecular genetic analysis of the chromosomes in infants with trisomy 21 determined that the majority of cases were attributable to maternal nondisjunction in meiosis I.
◦ Down syndrome is the most common triploidy (3n) in which individuals have three sets of chromosomes.
◦ There is a link between the increased risk of Down syndrome and increased maternal age at conception.
The Sun in false-color ultraviolet image
Down Syndrome Features
Korsakoff’s Syndrome
Cataracts seen in a child with congenital rubella syndrome.
Cushing’s syndrome
Pedigree of fragile X syndrome