Uncommon Descent Serving The Intelligent Design Community

At New Scientist: “single-celled organism that lacks most of the molecular equipment needed to kick-start DNA replication”


And it is a free-living protist, not a parasite:

“I was astonished,” says Dayana Salas-Leiva at Dalhousie University in Halifax, Canada. The microbe, Carpediemonas membranifera, must have a mechanism for copying its DNA that is unknown to science.

Michael Marshall, “Microbe somehow survives without key proteins for replicating its DNA” at New Scientist

It’s a protist? “Protists are a group of loosely connected, mostly unicellular eukaryotic organisms that are not plants, animals or fungi. There is no single feature such as evolutionary history or morphology common to all these organisms and they are unofficially placed under a separate kingdom called Protista.” In short, just the sort of life form that might be doing something really different.

Because nature is full of intelligence, there are probably many alternative programs out there. It all didn’t just somehow happen randomly once.

The paper is open access.



From the paper's Abstract: Cells must replicate and segregate their DNA with precision. In eukaryotes, these processes are part of a regulated cell-cycle that begins at S-phase with the replication of DNA and ends after M-phase. Previous studies showed that these processes were present in the last eukaryotic common ancestor and the core parts of their molecular systems are conserved across eukaryotic diversity. However, some unicellular parasites, such as the metamonad Giardia intestinalis, have secondarily lost components of the DNA processing and segregation apparatuses. To clarify the evolutionary history of these systems in these unusual eukaryotes, we generated a high-quality draft genome assembly for the free-living metamonad Carpediemonas membranifera and carried out a comparative genomics analysis. We found that parasitic and free-living metamonads harbor a conspicuously incomplete set of canonical proteins for processing and segregating DNA. Unexpectedly, Carpediemonas species are further streamlined, completely lacking the origin recognition complex, Cdc6 and other replisome components, most structural kinetochore subunits including the Ndc80 complex, as well as several canonical cell-cycle checkpoint proteins. Carpediemonas is the first eukaryote known to have lost this large suite of conserved complexes, suggesting that it has a highly unusual cell cycle and that unlike any other known eukaryote, it must rely on a novel set of mechanisms to carry out these fundamental processes. So, this protist "evolved" a new mechanism for DNA replication. Boy, that's something, right? And what did this obvious case of 'evolution" get us? I don't know: yeast becoming a parasite. The point is this: this is 'backwards' evolution. Well why didn't this protist 'evolve' to become a hummingbird? IOW, how did it get 'stuck'? Maybe only "devolution" is possible. PaV

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