**Core Concept**
Anticipation in genetics refers to the phenomenon where the symptoms of a genetic disorder become apparent at an earlier age as the disorder is passed down through generations. This is often seen in conditions where the genetic mutation is unstable and tends to expand, leading to a more severe expression of the disease.

**Why the Correct Answer is Right**
Trinucleotide repeat expansion is a type of genetic mutation that leads to anticipation. This occurs when a DNA sequence, typically consisting of three nucleotides (e.g., CAG), is repeated multiple times in a row. As this repeat sequence is passed down through generations, it tends to expand, resulting in a longer repeat length. This expansion can lead to a more severe expression of the disease, as the protein produced by the affected gene becomes toxic or non-functional. Examples of diseases caused by trinucleotide repeat expansion include Huntington's disease and fragile X syndrome.

**Why Each Wrong Option is Incorrect**
**Option A:** Translocation refers to the movement of a part of a chromosome to a different location in the genome. While translocations can lead to genetic disorders, they do not typically cause anticipation.

**Option B:** Chromosome breaking, or chromosomal fragmentation, occurs when a chromosome is broken into smaller pieces. This can lead to genetic disorders, but it is not typically associated with anticipation.

**Option D:** Mitochondrial mutation refers to a change in the DNA of the mitochondria, the energy-producing structures within cells. While mitochondrial mutations can lead to genetic disorders, they do not typically cause anticipation.

**Clinical Pearl / High-Yield Fact**
Anticipation is a key feature of trinucleotide repeat expansion disorders, and it is essential to recognize this phenomenon when assessing patients with suspected genetic disorders. This can help clinicians provide accurate diagnoses and genetic counseling to affected families.

**✓ Correct Answer: C. Trinucleotide - repeat expansion**