Did genomic imprinting and X chromosome inactivation arise from stochastic expression?
Both X chromosome inactivation and autosomal genomic imprinting generate a functional hemizygosity. Here we consider models that explain the evolution of genomic imprinting and X chromosome inactivation from novel perspectives. Specifically, we suggest that random (in)activation events are common in genes and gene clusters with a low probability of transcription. These generate variability that natural selection has acted on to evolve stable monoallelic expression. Possible selection forces might include a need for dosage compensation and the prevention of biallelic silencing where a total switch off would be lethal. Two different mechanisms can accomplish regular monoallelic expression - genomic imprinting and gene counting.
Ohlsson
R
R
Dept of Genetics and Development, Evolution Biology Centre, Uppsala University, Norbyvägen 18A, S-752 36 Uppsala, Sweden. Rolf.Ohlsson@ebc.uu.se
Paldi
A
A
Graves
J A
JA
D000818:Animals; D005075:Biological Evolution; D004303:Dosage Compensation, Genetic; D018392:Genomic Imprinting