HGT in Eukaryotes However, things are different for eukaryotes, such as animals, plants, and fungi. For most eukaryotes, germ cells are kept separate from somatic cells [2–3]. This means that if a foreign gene ends up in a somatic cell, it won’t be passed down to the next generation; only genes that incorporate into sperms and eggs, or their progenitor cells (cells that will divide into sperms and eggs), can be inherited. Therefore, for HGT to have lasting effects in eukaryotes, it often has to happen in a germ cell. Still, HGT can occur in eukaryotes, and certain conditions seem to increase its likelihood. These include processes like phagocytosis, where cells engulf other cells or particles, and symbiosis, where two different organisms live in close association. HGT may also happen more frequently during early developmental stages when the organism only consists of one or a few unspecialized cells, such as when it is a spore, zygote, or embryo. Unlike bacteria, the main way foreign DNA becomes part of a eukaryotic genome is through a process called “non-homologous end joining.” This is a natural DNA repair mechanism that fixes breaks by directly connecting the broken ends of DNA. When foreign DNA is present during this repair process, it can sometimes be inserted into the genome. Although biologists haven’t reached a consensus on how common HGT is in eukaryotes, some fascinating examples have been documented. One involves an aphid ancestor acquiring carotenoid genes from fungi [5]. This was the first time a group of carotenoid genes was found in an animal genome. These pigmentproducing genes allow aphids to produce red, green, and yellow colors. In nature, red and green aphids are both common because predators and parasites tend 13 ng Tree? 演化樹真的是樹狀嗎？ Bacteria (and possibly archaea) can acquire “foreign” antibiotic resistance genes and other genetic materials through three main processes: transformation, transduction, and conjugation (figure 1). In transformation, bacteria take up naked DNA from their surroundings, often in the form of plasmids. Transduction involves the transfer of genes between bacterial hosts by bacteriophages, which are viruses that infect bacteria. DNA can also be transferred from one bacterium to another through conjugation, during which bacteria mate by forming a cellto-cell connection. HGT is so widespread among bacteria that researchers estimate that around one-third of all gene transfers in bacterial evolution happen this way [4]. Figure 1 llustration of the three major mechanisms of horizontal gene transfer in prokaryotes: transformation, transduction, and conjugation.
RkJQdWJsaXNoZXIy NDk5Njg=