Joined: May 2002
Niall Shanks, in particular, has argued that redundancy is an answer to Behe's arguments about irreducible complexity. Systems may evolve with multiple parts with redundant function, and then lose parts to produce and IC system. This is essentially the common "scaffolding" argument.
Compared to co-option and helpful-part-becomes-necessary, I think that redundancy elimination is a relatively minor player. However, it is worth gathering examples of the phenomenon in order to further evaluate this.
So, here is a starter example that I came across:
|J Bacteriol. 2004 Feb;186(3):646-53. |
Nine mutants of Chlorobium tepidum each unable to synthesize a different chlorosome protein still assemble functional chlorosomes.
Frigaard NU, Li H, Milks KJ, Bryant DA.
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA. firstname.lastname@example.org
Chlorosomes of the green sulfur bacterium Chlorobium tepidum comprise mostly bacteriochlorophyll c (BChl c), small amounts of BChl a, carotenoids, and quinones surrounded by a lipid-protein envelope. These structures contain 10 different protein species (CsmA, CsmB, CsmC, CsmD, CsmE, CsmF, CsmH, CsmI, CsmJ, and CsmX) but contain relatively little total protein compared to other photosynthetic antenna complexes. Except for CsmA, which has been suggested to bind BChl a, the functions of the chlorosome proteins are not known. Nine mutants in which a single csm gene was inactivated were created; these mutants included genes encoding all chlorosome proteins except CsmA. All mutants had BChl c contents similar to that of the wild-type strain and had growth rates indistinguishable from or within approximately 90% (CsmC(-) and CsmJ(-)) of those of the wild-type strain. Chlorosomes isolated from the mutants lacked only the protein whose gene had been inactivated and were generally similar to those from the wild-type strain with respect to size, shape, and BChl c, BChl a, and carotenoid contents. However, chlorosomes from the csmC mutant were about 25% shorter than those from the wild-type strain, and the BChl c absorbance maximum was blue-shifted about 8 nm, indicating that the structure of the BChl c aggregates in these chlorosomes is altered. The results of the present study establish that, except with CsmA, when the known chlorosome proteins are eliminated individually, none of them are essential for the biogenesis, light harvesting, or structural organization of BChl c and BChl a within the chlorosome. These results demonstrate that chlorosomes are remarkably robust structures that can tolerate considerable changes in protein composition.
Articles/books by Shanks:
Shanks, Niall (2004). God, the Devil, and Darwin. Oxford University Press. Amazon.com
Shanks, Niall, and Joplin, Karl (2001). Behe, Biochemistry, and the Invisible Hand. Philo 4(1). URL: http://www.philoonline.org/library/shanks_4_1.htm
Shanks, Niall, and Joplin, Karl (2000). Of Mousetraps and Men: Behe on Biochemistry. RNCSE 20 (1-2): 25-30. Online at NCSE.
Shanks, Niall, and Joplin, Karl (2000). Redundant Complexity:A Critical Analysis of Intelligent Design in Biochemistry. Philosophy of Science 66 (June): 268-282. Online at ASA.