Single parent genes

Geneticists have long thought that for most human genes, alleles from both paternal and maternal chromosomes are equally expressed within a cell. But according to a study published this week in Science, the allelic contribution from either parent can be randomly turned off in more than five percent of genes. This mechanism may allow cells to generate phenotypic diversity from a common genome, the authors say. "Until this paper came out, it wasn't clear how widespread this phenomenon was," said Mark Bix of St. Jude Children's Research Hospital, who was not an author of the study. Researchers have previously observed non-random selection of only one allele--called monoallelic expression--in early embryonic development, in the processes of imprinting and X-inactivation. They have also found examples of random monoallelic expression in just a few genes in the immune or nervous system. Andrew Chess and colleagues at Harvard Medical School in Boston...