Welcome to the MedLibrary.org Wikipedia Supplement on Triangle of U -- Please Click to Return to Front Page

Triangle of U:Overview of genetic relationships between various members of the genus Brassica. Chromosomes from each of the genomes A, B and C are represented by different colours. The cartoon shows the origin of the AABB, AACC and BBCC species which have chromosome sets from their AA, BB and CC ancestors.

The Triangle of U is a theory about the evolution and relationships between members of the plant genus Brassica. It says that the genomes of three ancestral species of Brassica combined to create three of the common vegetables and oilseed 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 by Woo Jang-choon, a Korean botanist who was working in Japan (where his name was transliterated as "Nagaharu U" ¹). Woo made synthetic hybrids between the diploid and tetraploid species and examined how the chromosomes paired in the resulting triploids. His work was influenced by work by Kihara on the origin of bread or hexaploid wheat and its relationship to its diploid ancestors.^{citation needed}

The 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 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 sprout 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 be allotetraploid (contain four genomes, derived from two different ancestral species). (Data from molecular studies indicate that the three diploid species are themselves paleopolyploids).^{citation needed}

• 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

1. ^ http://junior.sciencetimes.co.kr/data/article/7000/0000006890.jsp (in Korean)

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).

Wikipedia content modification information:

• This page was last modified on 29 October 2008, at 22:25.

Wikipedia Authorship and Review

Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.

Wikipedia Usage Guidelines

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Triangle of U".

The URL for this specific entry is:

• http://medlibrary.org/medwiki/Triangle_of_U

All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.