What does genomic imprinting imply about alleles?

Genomic imprinting refers to a phenomenon where certain genes are expressed in a parent-of-origin-specific manner. This means that for these imprinted genes, only one allele (either the one inherited from the mother or the one inherited from the father) is active, while the other is silenced. This selective expression is a result of epigenetic marks, such as DNA methylation or histone modifications, that distinguish the parental alleles.

Option B correctly highlights that imprinted alleles have different expression patterns depending on their parental origin, which is a crucial aspect of the imprinting process. This selective gene expression has significant implications for development and can influence phenotypic traits.

In contrast, other options do not accurately describe genomic imprinting. The idea that certain alleles are expressed equally from both parents misrepresents the fundamental basis of imprinting, which focuses on the differences in expression. Random activation of all alleles is not a characteristic of genomic imprinting since it specifically involves preferential expression. Lastly, stating that alleles do not vary with parental origin overlooks the essence of imprinting, where the origin does play a critical role in gene expression.