Summary
Parent-of-origin-specific gene expression caused by epigenetic marks, as seen in IGF2 and H19.
In depth
For imprinted genes only one parental copy is expressed because of methylation set in the germline. Examples are IGF2 (paternal expression) and H19 (maternal). Disorders include Prader-Willi (paternal deletion of 15q11-q13) and Angelman syndrome (maternal deletion of the same region).
Imprinting violates the simple rule that both alleles contribute equally.
Imprinting evolved, according to the conflict hypothesis, because paternal genes favour growth of offspring and maternal genes limit demand to conserve resources. Methylation marks are erased in primordial germ cells and reset according to the sex of the parent.
Prader-Willi syndrome arises when the paternal copy of a region on chromosome 15 is missing, while Angelman syndrome results from loss of the maternal copy; the same deletion gives two different diseases depending on the parent of origin. Beckwith-Wiedemann syndrome involves overgrowth linked to IGF2 imprinting.
Frequently asked questions
What is Genomic Imprinting?
Parent-of-origin-specific gene expression caused by epigenetic marks, as seen in IGF2 and H19.
Which area of biology covers Genomic Imprinting, and how advanced is it?
Genomic Imprinting is one of the 54 topics in Genetics. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include X-Chromosome Inactivation, Trinucleotide Repeat Disorders, Epigenetics.
Why does Genomic Imprinting matter?
Imprinting is the reason why mammals cannot develop from two maternal or two paternal genomes, so parthenogenesis does not occur.
Can you give an example of Genomic Imprinting?
In mammals, uniparental embryos fail, showing that both parents' genomes are required.
What should I learn before Genomic Imprinting?
Work through the Beginner topics in Genetics first, such as Heredity, Gene, Allele, then return to Genomic Imprinting. Advanced topics assume the Intermediate vocabulary.
What topics are related to Genomic Imprinting?
The closest topics to Genomic Imprinting are X-Chromosome Inactivation, Trinucleotide Repeat Disorders, Epigenetics, Hybrid Vigour. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Genomic Imprinting?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Genomic Imprinting. To practise the whole of Genetics, use the Genetics quiz.
How is Genomic Imprinting different from X-Chromosome Inactivation?
Genomic Imprinting: Parent-of-origin-specific gene expression caused by epigenetic marks, as seen in IGF2 and H19. X-Chromosome Inactivation: One X chromosome in each female cell is silenced as a Barr body to equalise gene dosage. Read both side by side and note what each one explains.
How should I study Genomic Imprinting step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with X-Chromosome Inactivation and explain the difference aloud. Finally, take the Genetics quiz and come back to this page for any question you miss.