hy are triplet repeat expansion disorders described as having dynamic mutations

Triplet repeat expansion disorders are described as having dynamic mutations due to the following reasons:

1. Variable Repeat Number: The term "dynamic" refers to the variability in the number of triplet repeats. In these disorders, the number of repeats can increase from one generation to the next. This is different from most genetic mutations, which remain stable across generations.

2. Instability of Repeats: The triplet repeats are unstable, meaning they can expand in number during a person's lifetime. This can occur during DNA replication, where the DNA polymerase can slip and cause an increase in the number of repeats. This instability can lead to a worsening of symptoms over time or the appearance of symptoms in individuals who were previously asymptomatic.

3. Anticipation Phenomenon: There is a phenomenon known as anticipation in these disorders, where the symptoms become more severe or appear at an earlier age in each successive generation. This is directly related to the increase in the number of triplet repeats.

4. Different Phenotypes: The number of repeats can also influence the phenotype, or physical manifestation, of the disorder. For example, in Huntington's disease, a greater number of repeats can lead to an earlier onset and more severe symptoms.

5. Mosaicism: The dynamic nature of these mutations can also lead to mosaicism, where different cells in the same individual have a different number of repeats. This can lead to variability in the symptoms and severity of the disorder within the same individual.

In summary, the term "dynamic" in the context of triplet repeat expansion disorders refers to the variable and unstable nature of these mutations, which can lead to a range of different phenotypes and a progression of symptoms over time.