- Triangle of U
The Triangle of U is a theory about the evolution and relationships between members of the
plant genus "Brassica ". It says that thegenomes of three ancestral species of "Brassica" combined to create three of the commonvegetables andoilseed crop species that we know today. The theory has since been confirmed by studies of DNA and proteins.The theory was first published in
1935 byWoo Jang-choon , a Koreanbotanist who was working inJapan (where his name was transliterated as "Nagaharu U" [http://junior.sciencetimes.co.kr/data/article/7000/0000006890.jsp (in Korean)] ). Woo made synthetic hybrids between thediploid andtetraploid species and examined how the chromosomes paired in the resulting triploids. His work was influenced by work byKihara on the origin ofbread or hexaploidwheat and its relationship to its diploid ancestors.Fact|date=July 2008The triangle shows how three of the "
Brassica " species were derived from three ancestral genomes, denoted by the letters AA, BB, or CC. Alone, each of these diploid genomes produces a common "Brassica" species. The letter "n" denotes the number ofchromosomes in each genome, and is the number found in the pollen or ovule. For example "Brassica rapa" has an A - n=10 (alternatively AA - 2n=20) designation. That means each somatic cell of the plant contains two complete genome copies (diploid) and each genome has tenchromosome s. Thus each cell will contain 20 chromosomes; since this is the diploid number it is written as 2n = 2x = 20.* AA - 2n=2x=20 - "
Brassica rapa (syn. Brassica campestris)" -Turnip ,Chinese cabbage
* BB - 2n=2x=16 - "Brassica nigra " -Black mustard
* CC - 2n=2x=18 - "Brassica oleracea " -Cabbage ,kale ,broccoli ,cauliflower These three species exist as separate species. But because they are closely related, it was possible for them to interbreed. This
interspecific breeding allowed for the creation of three new species of tetraploid "Brassica". Because they are derived from the genomes of two different species, these hybrid plants are said to beallotetraploid (contain four genomes, derived from two different ancestral species). (Data from molecular studies indicate that the three diploid species are themselvespaleopolyploid s).Fact|date=July 2008* AABB - 2n=4x=36 -"
Brassica juncea " -Indian mustard
* AACC - 2n=4x=38 -"Brassica napus " -Rapeseed ,rutabaga
* BBCC - 2n=4x=34 -"Brassica carinata " -Ethiopian mustard References
Notes
Bibliography
* N. U. "Genome analysis in Brassica with special reference to the experimental formation of B. napus and peculiar mode of fertilization."
Japanese Journal of Botany 7: 389-452 (1935).
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