Another genome from a single-celled organism has been sequenced. This time it is the green algae, Chlorella. Chlorella are tiny algae that can reproduce quite rapidly. Yet despite the stream-lined nature of the organism, it retains most of the phytohormone biosynthesis pathways necessary to the development and growth of land plants.
Check it out:
Another interesting feature of the NC64A genome was the presence of homologs of receptors and biosynthetic enzymes of land plant hormones, such as abscisic acid, auxin, and cytokinin. The presence of these homologs does not necessarily imply the existence of plant hormones and their related functions in Chlorella but supports the hypothesis that genes involved in phytohormone biosynthesis and perception were established in ancestral organisms prior to the appearance of land plants.
Not only does this genome add more evidence to the growing plausibility of front-loading, but it also seems to offer a clue that the horizontal transfer of genetic information played a key role in the evolution of one of its key features – it’s unique chitin cell wall.
In the previous posting, I tried to help you visualize pseudogenes from a teleological perspective, demonstrating that the non-teleological perspective is not necessary. Let’s take it a step further.
Pseudogenes are sequences of DNA that are similar to functional genes, but have acquired defects that prevent the expression of functional products. Such sequences are generated by gene duplication, where one duplicate undergoes some lesion that is not selected against. As a result, the defective gene (now a pseudogene) may continue to undergo further mutational insult, effectively causing it to decay into oblivion over time.
Yet because the cellular architecture entails that an “RNA world” exists in parallel with a “protein world,” might many of these pseudogenes simply be genes escaping the constraints of the protein world in order for the opportunity to more fully participate in the RNA world?
Over at BioLogos, Dennis Venema and Darrel Falk have written a nice summary of pseudogenes and how they relate to our understanding of common descent. But we can take their discussion to a deeper level to help you better appreciate pseudogenes from a teleological perspective.
Posted in DNA, genomes
Tagged DNA, genome
I’ve combined the essays about the signal recognition partcle, Alu elements, cytosine deamination, all connected by front-loading. All 11, 465 words of it.
It’s often the case that I get an idea but don’t have the time to write up a decent blog to spell it out. As a result, some ideas come and go. So I will start a new tag entitled, FLE ruminations. Here I will jot down ideas for possible future reference and/or expansion. We’ll kick it off with some stuff that is in the process of connecting genomic shape to front-loading:
I’ve been talking about Alu elements for weeks now, so I was going to try to change the topic. But alas, I can’t stop myself. Here is some more Alu Fun for those similarly intrigued by the manner in which these nifty reformatting devices can facilitate evolution.
First, here is a decent video that outlines the basics of Alu retrotansposition.
Second, remember how it has become clear that the genome has a three-dimensional architecture?