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The triangle of U is a theory about the evolution and relationships between members of the plant genus ''Brassica''. The theory states that the genomes of three ancestral species of ''Brassica'' combined to create three of the common modern vegetables and oilseed crop species. It has since been confirmed by studies of DNA and proteins. The theory was first published in 1935 by Woo Jang-choon, a Korean-Japanese botanist who was working in Japan (where his name was Japanized as "Nagaharu U", the Japanese reading of his name).〔http://junior.sciencetimes.co.kr/data/article/7000/0000006890.jsp (in Korean)〕 Woo made synthetic hybrids between the diploid and tetraploid species and examined how the chromosomes paired in the resulting triploids. ==Overview== The triangle of U is illustrated by the triangular diagram on the right. It 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 of chromosomes 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 ten chromosomes. 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, Brussels sprouts, cauliflower, kohlrabi These three species exist as separate species, but because they are closely related, it was possible for them to interbreed. Unfortunately inbreeding within the species does not produce genomes that are resistant to unregulated contamination. 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 be allotetraploid (contain four genomes, derived from two different ancestral species). (More specifically, they are amphidiploid, i.te., containing one diploid genome from each of the two different ''Brassica'' species). Data from molecular studies indicate the three diploid species are themselves paleopolyploids. * AABB – 2n=4x=36 – ''Brassica juncea'' – Indian mustard * AACC – 2n=4x=38 – ''Brassica napus'' – rapeseed, rutabaga * BBCC – 2n=4x=34 – ''Brassica carinata'' – Ethiopian mustard 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Triangle of U」の詳細全文を読む スポンサード リンク
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