Is this the beginning of the end of plant...(plete copy of the chromosome. The double...)

Date:6/8/2009

plete copy of the chromosome. The double-chromatid chromosomes line up along the centre of the cell. In mitosis, the two chromatids are pulled apartthe X is divided along one axis of symmetryand these then pass into two genetically identical daughter cells. In meiosis, there are two lining up and dividing phases. The first lining up is of homologous chromosomesall chromosomes in an adult cell have a partner, members of the partnership coming from the mother and father of the celland these homologous chromosomes are each made up of two chromatids. The first division divides homologous pairs of chromosomes while the second meiotic division is just like the mitotic di vision: the chromosomes line up at the middle of the new cell and the chromatids divide at the centre of the X.

Thus the differences between mitosis and meiosis are that meiosis has two rounds of division; co-segregation of sister chromatids at the first division; and recombination that occurs during the first divisiona swapping over process that adds more genetic diversity to offspring. The new work, led by Raphael Mercier, identifies a gene that controls one of these three featuresentry into the second meiotic divisionin the sexual plant Arabidopsis thaliana. By combining a mutation in this gene with two other previously described mutationsone that eliminates recombination and another that modifies chromosome segregationthe authors have created a strain of plant (called MiMe for 'mitosis instead of meiosis') in which meiosis is totally replaced by mitosis.

MiMe plants produce pollen and eggs that are genetically identical to their parent. If MiMe eggs are self-fertilized by MiMe sperm, the offspring plant has twice as much DNA as the parent generation, and has all the genes from this single parent.

Thus the authors have made a form of asexual reproduction possible in a normally sexual species. Turning meiosis into mitosis is not enough to reach clonal reproduction, but it's
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Contact: Sally Hubbard press@plos.org Public Library of Science Source:Eurekalert

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