Passion cebulice zafrana in jesenskega podleska vsebujejo alkaloid Colchicine. Belivitez ti se pa ne smej ce nimas pojma
Colchicine inhibits microtubule polymerization by binding to tubulin, one of the main constituents of microtubules. Availability of tubulin is essential to mitosis, and therefore colchicine effectively functions as a "mitotic poison" or spindle poison.
The mitosis inhibiting function of colchicine has been of great use in the study of cellular genetics. To see the chromosomes of a cell under a light microscope, it is important that they be viewed near the point in the cell cycle in which they are most dense. This occurs near the middle of mitosis, so mitosis must be stopped before it completes. Adding colchicine to a culture during mitosis is part of the standard procedure for doing karyotype studies.
Apart from inhibiting mitosis (a process heavily dependent on cytoskeletal changes), colchicine also inhibits neutrophil motility and activity, leading to a net anti-inflammatory effect.
Since chromosome segregation is driven by microtubules, colchicine is also used for inducing polyploidy in plant cells during cellular division by inhibiting chromosome segregation during meiosis; half the resulting gametes, therefore, contain no chromosomes, while the other half contain double the usual number of chromosomes (i.e., diploid instead of haploid, as gametes usually are), and lead to embryos with double the usual number of chromosomes (i.e., tetraploid instead of diploid). While this would be fatal in animal cells, in plant cells it is not only usually well tolerated but in fact frequently results in plants that are larger, hardier, faster-growing, and in general more desirable than the normally diploid parents; for this reason, this type of genetic manipulation is frequently used in breeding plants commercially.
When such a tetraploid plant is crossed with a diploid plant, the triploid offspring will usually be sterile (unable to produce fertile seeds or spores), although many triploids can be propagated vegetatively. Growers of annual triploid plants not readily propagated must buy fresh seed from a supplier each year. Many sterile triploid plants, including some tree and shrubs, are becoming increasingly valued in horticulture and landscaping because they do not become invasive species. In certain species, colchicine-induced triploidy has been used to create "seedless" fruit, such as seedless watermelons (Citrullus lanatus). Since most triploids do not produce pollen themselves, such plants usually require cross-pollination with a diploid parent to induce fruit production.
Colchicine's ability to induce polyploidy can be also exploited to render infertile hybrids fertile, for example in breeding triticale (× Triticosecale) from wheat (Triticum spp.) and rye (Secale cereale). Wheat is typically tetraploid and rye diploid, with their triploid hybrid infertile; treatment of triploid triticale with colchicine gives fertile hexaploid triticale.
When used to induce polyploidy in plants, colchicine cream is usually applied to a growth point of the plant, such as an apical tip, shoot, or sucker. Also, seeds can be presoaked in a colchicine solution before planting. Another way to induce polyploidy is to chop off the tops of plants and carefully examine the regenerating lateral shoots and suckers to see if any look different. If no visual difference is evident, flow cytometry can be used for analysis.
Doubling of plant chromosome numbers also occurs spontaneously in nature, with many familiar plants being fertile polyploids. Natural hybridization between fertile parental plants of different levels of polyploidy can produce new plants at an intermediate level, such as a triploid produced by crossing between a diploid and a tetraploid, or a hexaploid produced by crossing between a diploid and an octoploid.
ce veste kaj je mitoza potem vse jasno
drugace pa prvo prebrat osnove delitve celic. Hektor se je igral s tem vem ker sva se menla. V praksi vecina semen umre, nekaj je normalnih in nekaj je mutantov, samo je to metoda hit and miss, vprasanje koliko semen rabis da dobis kar si zelel. Si pa tukaj ze na podrocju GMO (gensko modificirani objekti)
police in helicopter search for marihuana ...