Anticipation is seen in-
**Core Concept**
Anticipation is a genetic phenomenon where a mutation in a single allele of a gene leads to an increased risk of developing a specific disorder. This occurs due to the anticipation of a more severe phenotype in subsequent generations, often associated with an expansion of trinucleotide repeats.
**Why the Correct Answer is Right**
Anticipation is primarily observed in genetic disorders caused by trinucleotide repeat expansions, such as Huntington's disease, myotonic dystrophy, and fragile X syndrome. The expansion of these repeats leads to an increased number of repeats in subsequent generations, resulting in a more severe clinical presentation. This is due to the toxic gain-of-function of the expanded repeats, which disrupts normal gene function and leads to the development of the disease.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because anticipation is not typically associated with chromosomal abnormalities or point mutations. While these types of mutations can lead to genetic disorders, they do not typically result in the expansion of trinucleotide repeats.
**Option B:** This option is incorrect because genetic predisposition is a broader concept that encompasses many different genetic phenomena, including anticipation. While genetic predisposition is related to anticipation, it is not a specific example of anticipation.
**Option C:** This option is incorrect because somatic mosaicism refers to the presence of two or more populations of cells with different genotypes in the same individual. This is not related to the concept of anticipation, which involves the expansion of trinucleotide repeats in subsequent generations.
**Option D:** This option is incorrect because germ-line mutation refers to a mutation that occurs in the germline cells (sperm or egg) of an individual. While germ-line mutations can lead to genetic disorders, they do not typically result in the expansion of trinucleotide repeats and are not a specific example of anticipation.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that anticipation is a specific type of genetic phenomenon that is associated with trinucleotide repeat expansions. This is in contrast to other genetic phenomena, such as point mutations or chromosomal abnormalities, which do not typically result in the expansion of trinucleotide repeats.
**Correct Answer:** C.