As most microbes reproduce asexually, "species" are defined by differences in their DNA sequences. when the genome of soil microbe a is analyzed, long stretches of genes from multiple species of other soil microbial species are discovered. This indicates that the microbes present in the soil underwent transformation and transfection. Transformation, shown in the image, is the process of the prokaryotic nucleus taking up the foreign DNA from other microbes present in the environment. Tranfection is like transformation but for the eukaryotic cells.
Explanation:
Cancer occurs in dividing cells only because genetic materials divide into two equal portions during division. This process may be interrupted by carcinogenes or mutagenes to make mutate cells and then render them as cancer cells. In the brain, the cells are differentiated and there is no chance to start division, then how can cancer be found in the brain.