Anticipation

A remarkable phenomenon in which a genetic disease appears earlier appearance and with increased from with each succeeding generation.

Anticipation was once thought not to exist in genetics.

It was chalked off as a meaningless statistical artifact.

However, anticipation has now been proven to occur in a large number of important genetic disorders, including Huntington disease and myotonic dystrophy.

In molecular terms, anticipation is due to the expansion of a trinucleotide repeat sequence in the DNA.

This phenomenon also occurs in the fragile X syndrome, the most common inherited form of mental retardation