Table 1.

Genotype Frequencies of Dihydrofolate Reductase 19-Base Pair Deletion and Serine Hydroxymethyltransferase C1420T Polymorphisms in Individuals with Down Syndrome

	Genotype frequencies n (%)
DHFR
II	20 (23.3)
ID	48 (55.8)
DD	18 (20.9)
SHMT
CC	41 (46.1)
CT	39 (43.8)
TT	9 (10.1)

I, allele without 19-bp deletion; D, allele with 19-bp deletion; C, wild-type allele; T, polymorphic allele.