Answer:
Triple repeat expansion.
Step-by-step explanation:
Fragile X syndrome is the genetic disorder in which the toxic RNA is produced in the body. This mutation is located on the long arm of the X chromosome.
Fragile X syndrome is also known as trinucleotide repeat disorders. The nucleotide CCG is increased in the affected individual from 200 to 4000. The severity of the disease depends on the repeat of CCG nucleotide in the individual.
Thus, the answer is triple repeat expansion.