USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

What is the primary effect of Germline Mosaicism on offspring?

1. Increased risk of somatic mutations

2. Inheritance of genetic mutation

3. Chromosomal translocations

4. Enhanced immune response

The correct answer is: Inheritance of genetic mutation

Germline mosaicism primarily affects offspring by leading to the inheritance of genetic mutations. In cases of germline mosaicism, an individual has a mixture of genetically different cells in their germline tissues (sperm or eggs). This means that while somatic cells may not express a particular mutation, some of the gametes can carry it. When one of these mutated gametes combines with a normal gamete from another parent during fertilization, this can result in the offspring inheriting the genetic mutation, despite the individual exhibiting a normal phenotype. This phenomenon is particularly significant when considering autosomal dominant disorders, where a mutation can be present in some germ cells but not within the somatic cells of the parent. Consequently, offspring may inherit these mutations more frequently than anticipated, which is a key aspect of genetic counseling in cases of germline mosaicism. The focus here is on how these mutations can pass to the next generation, directly impacting the genetic landscape of the offspring, which makes this option the most appropriate choice. Other options do not directly relate to the main impact of germline mosaicism on offspring.