In genetics,<unk> is a phenomenon whereby as a genetic disorder is passed on to the next generation, the symptoms of the genetic disorder become apparent at an earlier age with each generation. In most cases, an increase in the severity of symptoms is also noted.<unk> is common in trinucleotide repeat disorders, such as Huntington's disease and myotonic dystrophy, where a dynamic mutation in DNA occurs. All of these diseases have neurological symptoms. Prior to the understanding of the genetic mechanism for<unk>  it was debated whether<unk> was a true biological phenomenon or whether the earlier age of diagnosis was related to heightened awareness of disease symptoms within a family.
Anticipation 
Expressivity 
Variegation 
Compound heterozygosity
Heteroplasmy
Aplasia
Trisomy
Agenesis