What are the mechanisms of genomic imprinting?

Genomic imprinting typically occurs through DNA methylation, where one allele of the gene is methylated (silenced) while the other allele remains unmethylated (active). Genomic imprinting alters how genes work, affecting either their expression or the functionality of their products. This methylation process (known as stamping) involves the attachment of methyl groups to specific segments of DNA. Certain regions of DNA, known as imprinting control regions (ICRs), are methylated in a parent-of-origin-specific manner. This methylation pattern is established during gametogenesis and is maintained after fertilization, leading to differential expression of imprinted genes based on the parental origin of the allele. Imprinted genes are expressed from a single chromosome.