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.
For example, certain kinds of breast cancers are insulin sensitive, and thus eating a lot of carbohydrates (ironically like in a vegan diet) would cause your body to produce lots of insulin, making this an inefficacious strategy in reducing risk for those particular kinds of cancer.
One reason a vegan diet might not be optimal for people with rheumatoid arthritis is because of the potential for inadequate amounts of important nutrients, including calcium and vitamins D and B12. Vegan diets also exclude fish, including salmon and tuna, which are high in anti-inflammatory omega-3 fatty acids.