Mental retardation has affected several generations of a family, and most of the affected individuals have been males. The severity of mental retardation has increased with each passing generation. Genetic testing is performed, and about 20% of the males who have the genetic abnormality are unaffected. Which of the following mechanisms is most likely to produce this genetic condition?
选项：

A:Frameshift mutation
B:Missense mutation
C:Mitochondrial DNA mutation
D:Point mutation
E:Trinucleotide repeat mutation