In the context of a fully penetrant autosomal dominant gene mutation, what can explain the presence of wild-type alleles in affected individuals?

In the scenario of a fully penetrant autosomal dominant gene mutation, the presence of wild-type alleles in affected individuals can be attributed to recombination events. Recombination occurs during meiosis, where homologous chromosomes exchange segments of genetic material. This process can lead to the formation of gametes that contain both a mutant allele and a wild-type allele.

When fertilization occurs, the resulting offspring can inherit one allele from each parent. In an individual affected by a dominant condition, if recombination has led to the preservation of the wild-type allele alongside the mutated one on different chromosome copies, both alleles may be present in the organism's genotype. Although the dominant mutation typically dictates the phenotype, the presence of the wild-type allele can still be detected through genetic testing or allele-specific analyses.

Understanding the role of recombination events helps clarify how, despite the dominance of a pathogenic allele, the wild-type allele can coexist in an affected individual’s genetic makeup.