This is due to sex-specific epigenetic imprinting; the biochemical mechanism is DNA methylation. This condition is associated with genetic imprinting. Natural selection for genomic imprinting requires genetic variation in a population. DNMT3A is essential for genetic imprinting. Appropriate imprinting of certain genes is important for normal development. Genomic imprinting and uniparental disomy, however, may affect inheritance patterns. This technique is of particular usefulness for genomic imprinting analysis. Methylation, along with histone modification, is central to imprinting. Genomic imprinting may also contribute to ASD. A widely accepted hypothesis for the evolution of genomic imprinting is the "parental conflict hypothesis". The study attempted to distinguish conceptually phenotypic matching from positive sexual imprinting. In insects, imprinting affects entire chromosomes. DNMT3L is expressed during gametogenesis when genomic imprinting takes place. These parent-of-origin effects reflect the effects of genomic imprinting. The process consists of imprinting a metallic foil with an image.