[Short introduction to gene imprinting].
Genomic imprinting refers to the genetic non-equivalence of mammalian paternal and maternal genomes. It leads to differential marking of gene alleles in parental gamets. This marking leads to differential expression of imprinted genes during embryonal development and in adult life. Usually one allele of an imprinted gene is active while the other is silent. Genomic imprinting renders mammals haploid for imprinted genes and thereby causes certain genetic diseases. These can be due to a variety of genetic events, such as loss or mutation of the active imprinted gene allele, disruption of imprinting in parental gamets so that both alleles are imprinted in the same way, or inheritance of a chromosome or part of chromosome bearing imprinted genes from a single parent. Several severe human genetic disorders are associated with imprinted genes, including Beckwith-Wiedemann, Prader-Willi and Angelman syndromes. In this review a glimpse of the complexity of genetic mechanisms, which lead to the differential transcription of imprinted genes, is presented.
Romer
J T
JT
Institute of Cancer Reaearch, Chester Beatty Laboratories, London SW3 6JB.