Definition- Genomic imprinting refers to an epigenetic marking of genes that results in monoallelic expression.
The parent-of-origin dependent phenomenon is a notable exception to the laws of Mendelian genetics. The law of equivalence as provided by Mendel is not universal. This law might be applicable to some genes within the same animal and may not be applied to other genes or chromosomes.
for example, the sex-chromosomes in the human beings. The male sex chromosomes have a different phenotypic effect compared to the female sex chromosomes. A number of genes have “imprinted or “stamped’ sex markers, which is male or female, though they are responsible for a same trait. This leads to a condition where the gene for a same character from a female and male have different behavior. This situation is an exception to the law of equivalence and the phenomenon is called Genetic Imprinting.
Genetic imprinting is also termed as Genome imprinting. It can be seen both in autosomes and sex chromosomes.
Imprinted genes are intricately involved in fetal and behavioral development. Consequently, abnormal expression of these genes results in numerous human genetic disorders including carcinogenesis.