imprinting
Frésard L, Morrison M, Brun J-M, Collin A, Pain B, Minvielle F & Pitel F 2013 Epigenetics and phenotypic variability: some interesting insights from birds. Genet Sel Evol 45:16.
- in the chicken and quail, many parent-of-origin QTL have been detected
- such studies can detect spurious QTL due to linkage disequilibrium or bias generated by the experimental design
- less than 200 imprinted genes were described
- a transcriptome sequencing approach reported in 2010 [49] uncovered parent-of-origin allelic effects for more than 1300 loci in the mouse
- this large number is the subject of much debate
- to date, no consensus on the number of imprinted genes in mammals has been reached
- replication of the chicken orthologs of some imprinted genes is asynchronous [65], even when they are biallelically expressed
- mammalian imprinted gene clusters originate from an ancestor common to all vertebrates
- they evolved from preimprinted to imprinted regions
- since the orthologous mammalian imprinted genes are biallelically expressed in the chicken, it is impossible to strictly link the asynchronous replication to imprinting in birds
