In bacterium, horizontal transfer is a common practice. As a lint brush picks up cat hair, the teeming single-celled organisms that populate most of the planet pick up genes from their environment. Natural selection ensures that the resistantbacteria out compete their neighbors and pass their genes on to the next generation. Some scientists think thatbacteria form a web of related life rather than a branching family tree, because they swap genes so easily.
Humans, Frogs and Snakes have different cells. The cell nucleus is a fortress for the genome. The citadel has a library where the genes that need to be examined are kept. The cell has fail-safes in it to prevent damage to its genetic material. The librarians carry swords if the genome is worth anything.
There are examples in the scientific literature of horizontal genes being transferred. herrings and smelts, unrelated fish that swim in the icy waters of the northern Pacific and northern Atlantic oceans, have the same genes that keep their blood from freezing. The work of Laurie Graham and her colleagues at Queen's University in Canada was so counterintuitive that it was difficult to get it published.
A group of biologists at the National Research Institute for Agriculture, Food and Environment in France are studying a set of worms that got their genes frombacteria. In a paper this year, Jinling Huang of Eastern Carolina University and colleagues wrote that over 100 gene families seem to have jumped from microbes to plants.
Some of these transfers were smiled on by evolution. The fish with the genes are not cold. The nematodes are able to get more energy from the cells of the plants they eat. The hot spring-dwelling red algae can survive contact with substances that would otherwise kill them because of a cluster of enzymes picked up frombacteria. It takes a long time for the descendants of the first organisms to take over.
Some of the wandering genes may convey an advantage. BovB is a transposon that can jump around the genome. In a way, its jumps from snakes into frog are larger than normal. BovB isn't agene with a function in the traditional sense, it's just a bit of DNA that makes copies of itself Although the possibility of BovB benefiting the frog can't be ruled out, it's more likely that BovB persists through its own aggressive success This may help to explain why transposons like BovB are involved when other organisms have the same genes.
Heterogeneity of horizontal gene transfer in the other direction is vastly rare, as it might seem for it to be odd. Thebacteria don't want our genes Eukaryotic genes have structural features that make them less than perfect forbacteria.
The University of British Columbia has a Biologist who studies horizontal transfers.
Viruses can pick up genes from their host. Retroviruses have the ability to get into a host's cells and nucleic acids, and they can insert genetic material into the host's genomes. Remnants of retroviruses make up 8% of the human genome.
The transfer can go the other way as well. The first comprehensive analysis of horizontal gene transfers between viruses and eukaryotes was performed by a group of people. Host-to-viruses are more common than virus-to-host transfers. Heterogeneous gene transfers have been major drivers of evolution on both sides, as the Viruses often used the eukaryotic genes they acquired to become more effective at infecting their hosts, while the Eukaryotes used elements of the viral genes to create novel features or to regulate their metabolisms in
Some biologists believe that some horizontal gene transfers may be aided by Viruses. If viruses can pick up genes from their hosts, and if they can leave behind pieces of their genomes, it's possible that they could give them to another host.
Another puzzle about horizontal transfers could be solved if viruses were involved. The traveling genes need to clear a number of hurdles in order for the transfers to take place. They need to get from the donor species to the new one. They need to get into the nucleus of the host genome. Getting into the genome of just any cell won't do: In multicellular creatures like frog and herrings, a gene won't be passed down to the animal's offspring unless it can sneak into a germ line cell.
It's possible that the series of events could be made more likely by viruses. The reproductive tract and germ cells of small organisms, like the nematode, are not far away from the intestinal tract, which can be a breeding ground for viruses. Frogs release their eggs and sperm into the open water, which could expose the cells to Viruses that could slip in genes.
It may be easier than you think. It is still a speculative idea, but the reproductive tract is full of germs. It's known that some viruses can cause germ cells.
In order to understand the mystery of horizontal gene transfer, we should think of them as ecological consequences of an organisms behavior, neighbors and environment. If a recipient of a horizontally transferred gene finds itself in an icy sea, a hot spring, or a plant with tough defenses, it is likely to confer any survival benefit. He speculated that they were tied to the ecology but it changed. The transferred genes are no longer beneficial with the wrong shift.
In the pond in your backyard, in the soil beneath your feet, in the animals, and in the plants, horizontal gene transfers may be happening all the time. There is a lot more transfer than we know. They are swept out, so we don't see them.
The team reached out to their colleagues for samples of frog from around the world to see how common snake BovB is. 50 of 149 species returned with BovB. The Malagasy frog that they tested made up less than a quarter of all the species they studied, but 29 of them carried the snake genes, which is a majority of all the transfers found around the world. Two of the frog lineages didn't acquire BovB until after their ancestors migrated from Africa to the island.
The paper shows the rate of transfer isn't uniform. It varies from region to region. What we find may surprise us if more studies set out with the goal of looking at gene transfer around the globe. Maybe geography is more important than we think.
Is it because of the environment of the island that it is a hot spot for gene transfers? Nobody knows. The group believes that the BovB in Madagascar is a little bit better at getting into a new host than it is in other places.
The island has a lot of parasites. The author of the new paper said that there are lots of leeches in Madagascar. You will see them if you are in the rainforest. Frogs and snakes are some of the animals that the blood sucking creatures feed on. According to Vences and his colleagues, the jumping genes of snakes may be brought into the frog by the leeches. It's possible that a virus does the rest.
It is difficult to prove or disprove scenarios about horizontal transfers. Without selection, they tend to change and get scrambled over long periods of time, which makes it hard to prove a transfer. Graham said that if a virus is involved in the transfer, it could leave very little evidence. It is possible that researchers need to catch a genetic jump in the act to understand how it is happening.
The early stages of the project aim to do that. He and his colleagues are looking for signs of transfers in the hot springs at Lemonade Creek. They are studying the genes frombacteria that live in the springs and redalgae that have picked up genes from other organisms. He said that they are not talking about millions of years ago. In the same environment, we are talking about DNA that is very similar to each other.
If the scientists find that the nearby springs don't have any of the transferred genes, then they may be witnessing the beginning of a domino effect. The hot pool may be an island on the verge of change.
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