Part 1 of Essay
is an dominant disorder characterized by myotonia, muscular dystrophy, cataracts, hypogonadism, frontal balding, and EKG changes. The discovery that the genetic defect is an amplified trinucleotide repeat in the 3-prime untranslated region of a protein kinase gene on chromosome 19 explains many of the unusual features of ....

Part 2 of Essay
.... generation - a phenomenon referred to as anticipation. Anticipation occurs more frequently when the gene is passed from mother to child rather than from father to child. Anticipation appears to be explained by the ability of the gene to expand from generation to generation. Amplification is frequently observed after parent-to-child transmission, but extreme amplifications are not transmitted through the male line. This explains anticipation and the occurrence of the severe congenital form almost exclusively ....