Whether or not the story is true, the symbolism of the thistle (ahem, sorry for the pun) took root and is honored to this day. Other facts about the thistle include that it is a biennial plant, meaning it takes two years to complete its life cycle. It reseeds easily. It's a combination of beauty and ruggedness. It has a spreading, invasive root system, hence its classification as weed.
imprinted gene, a gene whose expression has been affected by genomic imprinting so that only a single allele functions, the other being turned off by epigenetic mechanisms during embryonic development.
A gene is considered to be imprinted if only the copy inherited from the mother or from the father is expressed throughout life. But one imprinted gene, Dlk1, disobeys this rule during postnatal neurodevelopment.See Letter p.381. 1  Stem cells â¢.n absence of imprinting in the neurogenic niche is a novel and unexpected concept, because it underscores an underappreciated functional link between epigenetic regulation, in the form of gene imprinting (and the removal thereof), and developmental events such as adult NSC homeostasis.