Dihydrofolate Reductase (DHFR) del19bp Polymorphism and Down Syndrome Offspring.

Down syndrome (DS) is the most common form of mental disability of genetic etiology. Nondisjunction of chromosome 21 is the leading cause of the syndrome. In general, free trisomy 21 cases originate from missegregation in maternal meiosis.

Betaine-homocysteine methyltransferase 742G>A polymorphism and risk of down syndrome offspring in a Brazilian population.

Down syndrome (DS) is the most common form of mental retardation of genetic etiology. Several polymorphisms in genes involved with the folic acid cycle have been associated to the risk of bearing a DS child; however, the results are controversial. Betaine-homocysteine methyltransferase (BHMT) is a key enzyme of folate pathway, and catalyzes the remethylation of homocysteine into methionine.

Haplotype analysis of the CAG and CCG repeats in 21 Brazilian families with Huntington's disease.

We studied the allelic profile of CAG and CCG repeats in 61 Brazilian individuals in 21 independent families affected by Huntington's disease (HD). Thirteen individuals had two normal alleles for HD, two had one mutable normal allele and no HD phenotype, and forty-six patients carried at least one expanded CAG repeat allele. Forty-five of these individuals had one expanded allele and one individual had one mutable normal allele (27 CAG repeats) and one expanded allele (48 CAG repeats).