Quote:
Originally Posted by Biochemist
I am pretty familiar with episomal tranfer (I am a Doctor of Pharmacy). This process does distribute some genes across a heterogeneous population, but it certainly does not move the population toward homogeneity.
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Excellent coverage on this from
Carl Zimmer over at
The Loom:
Quote:
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Originally Posted by Zimmer
Festooning The Tree Of Life | The Loom | Discover Magazine
Bacteria and other single-celled microbes make up much more of life’s genetic diversity, and they were around for three billion years before animals showed up for the party. So much of the history of life may not fit the tree metaphor very well any more. No longer can we assume that the genes in a species all have the same history. Some of them may have leaped from species to species.
So how should we picture the history of life then? The newest assault on this tough question just came out in the Proceedings of the National Academies of Sciences. Tal Dagan, a biologist at the University of Dusseldorf, and her colleagues have festooned the tree of life with lateral gene transfer. They analyzed 539,723 genes from the completely sequenced genomes of 181 species of microbes. To begin making their new picture of evoluiton, they drew a tree showing how those 181 species are related. They used a gene that doesn’t seem to have been traded around much, and which therefore reflects the common descent of the microbes.
[...]
Analyzing this tree bush mangrove thicket Gordian knot, Dagan and her colleagues found a fascinating interplay between vertical and lateral gene transfer. If you look at any one of the 181 genomes, 81% on average of its genes experienced lateral gene transfer at some point in its history. So clearly lateral gene transfer is rampant. But once genes made the jump, they tended not to make another one–in fact, Dagan and her colleagues conclude that most became trapped in vertical descent.
This new picture is a far cry from Darwin’s sketch, and thank goodness for that. A science that doesn’t move forward for 150 years isn’t much of a science at all. But we may need some new metaphors to help us catch up with it.
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Click to view excellent images from the study in the above post.
The image in this post is more interesting(imo) as it contains a bit more content:
Quote:
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Originally Posted by Zimmer
Tangling the Tree | The Loom | Discover Magazine
This picture is a splendid representation of this debate. Scientists at the European Bioinformatics Institute created it by comparing 184 microbes. The scientists first identified genes that the microbes all inherited from a common ancestor that they then passed down in conventional parent-to-offspring fashion. By comparing their different sequences, the scientists were able to draw a conventional tree of the sort Darwin had in mind. Next, they scanned the genomes of these microbes for jumping genes. They drew the jumpers as vines from one branch to the next. They then produced this three-dimensional picture.
As you can see, the branches rise from a common ancestor, but they are enmeshed in vines. What’s particularly fascinating about it is the way in which the vines connect the branches. It is not a random mesh. Instead, a few species are like hubs, with spokes radiating out to the other species. This is the same pattern that turns up in many networks in life, from the genes that interact in a cell to the nodes of the Internet. These hubs can bring a vast number of nodes into close contact. It’s why you can play Six Degrees of Kevin Bacon. In the microbial world, this network allows genes to move quickly through the tree of life, whether those genes provide resistance to antibiotics or allow microbes to cope with some other change in the environment. The Kevin Bacons of the microbial world, at least in the current study, seem to be species that live in habitats where they may come in intimate contact with other species, such as in plant roots. They then act as gene banks from which other species can make withdrawals.
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Also, I didn't directly link to this in my previous posts, but to anyone who hasn't seen it here is a link to the relevant
court rulings on
Intelligent Design from
Kitzmiller v. Dover Area School District.
Also, recently
Ken Miller guest blogged over at The Loom further
debunking Intelligent Design. Probably of interest to anyone following this thread:
Smoke and Mirrors, Whales and Lampreys: A Guest Post by Ken Miller | The Loom | Discover Magazine
Ken Miller’s Guest Post, Part Two | The Loom | Discover Magazine
Ken Miller’s Final Guest Post: Looking Forward | The Loom | Discover Magazine
