The results of the study indirectly confirm the hypothesis of the “night of a bottleneck”.
Somalian cave fish that lived in darkness the last three million years, lost the ability to photoreactive. This recovery mechanism of DNA damage caused by ultraviolet radiation and it is missing not only cave fishes but also the placental mammals. As stated in Current Biology, the results of the study indirectly confirm the hypothesis of the “night of a bottleneck”, according to which mammals have adapted to the daily way of life only after the extinction of dinosaurs, informs Rus.Media.
DNA repair – the restoration of tears and chemical damage that can occur in the biosynthesis of DNA, and under the influence of other factors, such as harmful chemicals or ultraviolet radiation. Under the action of ultraviolet light, some of the nucleotides of DNA are sewn together. As a result, in the copying of DNA enzymes nucleotides are read incorrectly, and this leads to the accumulation of mutations. To fix these crosslinked nucleotides by using photoreactive, during which the enzymes DNA-fotolii activated by visible light and remove the crosslinked nucleotides.
DNA fotolii, and, consequently, the ability to photoreactive is, in most animals, with the exception of placental mammals. Therefore, to repair DNA damage caused by ultraviolet radiation, they have to use more complex and less efficient mechanism of repair. Some researchers support the hypothesis of the “night of a bottleneck”, according to which the ancestors of modern placental, that lived at one time with dinosaurs were exclusively nocturnal. So they were saved from more powerful reptiles that were active during the day. The result is that the mammals have lost the ability to photoreactive that “runs” of visible light.
In the new study, German and Italian biologists led by Nicholas Foulkes (Foulkes Nicholas) from the Karlsruhe Institute of Technology studied the DNA repair system cave fish. These fish, endemic to Somalia, several million years living in caves in complete darkness. Like some other cave fish, in the course of evolution they have lost pigmentation and became blind. Scientists decided to find out how lack of sunlight affected the mechanisms of DNA repair.
Study of genes three DNA potholes Somali cave fish showed that two of them contained the mutation “turns off” the activity of these enzymes. In other fishes, zebrafish, nothing similar was observed.
According to the authors, the results of the study indirectly confirm the hypothesis of the “night of a bottleneck”. They suggest that mammals, and the Somalian cave fish have lost the ability to photoreactive for the fact that for millions of years, were forced to lead a nocturnal lifestyle.