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.
Genomic imprinting, also referred to as gametic or parental imprinting, was discovered almost simultaneously by two laboratories in 1984. Prior to the publications of McGrath and Solter (1984) and Surani et al.(1984), conflicting results existed about whether both parental genomes were required for normal development.a Aa Aa. In the majority of cases, two copies of each chromosome â and therefore, two copies of each gene â arrive in every fertilized egg. However, in some cases, one of the genes within a pair is somehow switched off; this occurs because of the process known as imprinting.