Chiasma (genetics) In genetics, a chiasma (pl. chiasmata) is the point of contact, the physical link, between two (non-sister) chromatids belonging to homologous chromosomes. At a given chiasma, an exchange of genetic material can occur between both chromatids, what is called a chromosomal crossover, but this is much more frequent during meiosis than mitosis. In meiosis, absence of a chiasma usually result in improper chromosomal segregation and aneuploidy.
A cancer prevention diet is one that is high in fiber, low in fat (especially animal fat), and includes generous portions of fruits and vegetables. It also minimizes or excludes alcohol. The best diets are pure vegetarian diets.
The more restrictive your diet is, the more challenging it can be to get all the nutrients you need. A vegan diet, for example, eliminates natural food sources of vitamin B-12, as well as milk products, which are good sources of calcium.With a little planning, however, you can be sure that your diet includes everything your body needs. This is because the vegan diet is rich in a vitamin called folate, which may mask deficiency in vitamin B-12 until severe problems occur. 2  For this reason, it's important for vegans to consider vitamin supplements, vitamin-enriched cereals and fortified soy products. 3  Vitamin D plays an important role in bone health.