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.
The significance of epigenetic mechanisms for gene regulation in cancer is now evident with cancer-related mechanisms acting at all epilayers. The study of epigenetic imprints is still in its infancy, as not all epigenetic marks are known, and only few of the known ones are understood in any detail.