What can lead to a differential expression of alleles in imprinting disorders?

The correct choice highlights the role of altered methylation patterns as a key factor in differential expression of alleles in imprinting disorders. In genomic imprinting, certain genes are expressed in a parent-of-origin specific manner due to epigenetic modifications, primarily DNA methylation.

When methylation patterns are altered, it can disrupt the normal expression of imprinted genes. Methylation typically serves to silence one allele of a gene that is expressed in a parent-specific manner. If the methylation pattern is lost or changed, it can lead to the expression of both alleles or the silencing of both alleles, resulting in various disorders. This is significant in conditions like Prader-Willi syndrome and Angelman syndrome, where the expression of genes from either the paternal or maternal allele is crucial for normal development.

Other options, while relevant to genetic variability or disorders, do not specifically address the mechanism of differential expression due to imprinting. For instance, homologous recombination relates to genetic exchange during meiosis and does not directly impact imprinting control. Gene duplication events usually focus on structural changes in the genome and can lead to gene dosage effects, but they don’t influence allele expression in an imprinting context. Environmental influences could affect gene expression broadly