Imprinted Genes Epigenetics

Excerpts- from a page on Imprinting


Imprinted genes are genes whose expression is determined by the parent that contributed them.

Imprinted genes violate the usual rule of inheritance that both alleles in a heterozygote are equally expressed.

Does advancing paternal age cause autism and schizophrenia, Alzheimer's and cancer because errors in imprinting result from age?


Is imprinting important?
Yes.
Deliberate (in mice) or accidental (in humans) inheritance of two copies of a particular chromosome from one parent and none from the other parent is usually fatal (even though a complete genome is present).
Inheritance of two copies of one of mother's genes and no copy of the father's (or vice versa) can produce serious developmental defects.
Failure to inherit several nonimprinted genes on the father's chromosome #15 causes a human congenital disorder called Prader-Willi syndrome.
Failure to inherit one nonimprinted gene (UBE3A) on the mother's chromosome #15 causes Angelman syndrome.
Failure of imprinting in somatic cells may lead to cancer.
The cancerous cells in some cases of a malignancy called Wilms´ tumor and many cases of colon cancer have both copies of the IGF2 gene expressed (where only one, the father's, should be).
Reduced methylation — and hence increased expression — of proto-oncogenes can lead to cancer, while
increased methylation — and hence decreased expression — of tumor suppressor genes can also do so.