Non-Linear Biology, Independent Convergence and Independent Solutions.
Convergent Evolution.
(RealPlayer, 56 min)
A seminar by Dr. Fazale Rana on "the surprising ability of nature to repeatedly arrive at nearly identical DESIGNS (e.g. the eye of the octopus and the vertebrate eye) without descent from a common ancestor."
(RealPlayer, 56 min)
A seminar by Dr. Fazale Rana on "the surprising ability of nature to repeatedly arrive at nearly identical DESIGNS (e.g. the eye of the octopus and the vertebrate eye) without descent from a common ancestor."
posted by fdocc | 9:31 PM
1 Comments:
I want to add the next references:
James A. Rosinski, William R. Atchley. Molecular Evolution of Helix–Turn–Helix Proteins. J Mol Evol (1999) 49:301–309.
"It has been hypothesized that the process of binding DNA is a relatively simple function for a gene to acquire and could have evolved many times, as independent solutions to a common problem of transcriptional regulation as evidenced by the zinc-finger, helix–loop–helix, and leucine zipper protein families (Struhl 1989; Pabo and Sauer 1992). This raises the question whether the highly divergent HTH proteins form an evolutionary lineage derived from a common ancestor or whether they are the result of the independent convergence upon an functionally active DNA-binding domain."
Struhl K (1989) Helix–turn–helix, zinc-finger, and leucine-zipper motifs for eukaryotic transcriptional regulatory proteins. Trends Biochem Sci 14:137–140.
Pabo CO, Sauer RT (1992) Transcription factors: Structural families
and principles of DNA recognition. Annu Rev Biochem 61:1053–
1095.
After that statement the authors continue:
"While it is conceivable that the 19 significantly similar subgroups of the HTH family arose through independent convergence, common ancestry followed by divergence is a much more likely mechanism."
The evidence that the authors presented "strongly suggests that prokaryotic and eukaryotic HTH proteins are homologous."
They mentioned "the failure of phylogenetic reconstruction."
And their view to postpone the issue because "only a longer region of conserved primary sequence or better models of the evolution of structural elements would improve the analysis. As the HTH motif is already well defined, it is doubtful that the length of the region to be analyzed can increase, and structural evolution models are still likely years away."
[Thanks to Dr. OAV for the reference!]
I also want to link to the next document for your personal study:
Thesis Manuscript , by Etienne Danchin. 2004. Reconstruction of Ancestral Genomic Regions by Comparative Analysis of Evolutionary Conserved Syntenies. Towards Reconstructing the Genome of the Ancestor of all Bilaterian Species (Urbilateria). Graduation as a Doctor in Bioinformatics, Structural Biology, and Genomics (BBSG). Université de la Méditerranée, Aix-Marseille II.
Where Etienne wrote:
"the hypothesis of convergence in this case would necessarily require more events, and for example, independent convergence should have occurred between Teleostean, cephalochordates, mammals, birds, and so on."
"the hypothesis of independent convergence necessarily implies that these genes are under a POSITIVE SELECTIVE pressure favoring them to cluster together and it should be notable when investigating for example expression pattern of these genes (as described in chapters 3.2 and
3.3)."
"we would favor the hypothesis of
independent convergence events that took place at least at the basis of dipterans on the one
hand and at the basis of euchordates on the other hand (as shown on Figure 19)."
"The likelihood of the hypothesis of conserved ancestral state compared to the one of independent convergence with POSITIVE SELECTION can still be discussed (as evoked in chapter
2.3.3), and we will present here a brief history of the debate between these two hypotheses for
the MHC and its three paralogous regions."
(Etc... for the word "convergence")
[Note: Words in Bold, my emphasis; CAPITALS, Etienne's emphasis]
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