Friday, May 19, 2006

DNA Repair: Part One

An excellent article entitled 'Life without DNA Repair' by David M. Wilson III and Larry H. Thompson can be accessed at the following address.

http://www.pnas.org/cgi/content/full/94/24/12754

Some snippets from the article and related comments follow.

"The advent of gene targeting techniques has permitted the construction of specific genetic deficiencies to evaluate the biological contribution(s) of an individual protein. Mice lacking a precise DNA repair activity have been generated, and these mutants show various combinations of defective embryogenesis, tissue-specific dysfunction, hypersensitivity to DNA-damaging agents, premature senescence, genetic instability, and elevated cancer rates (1). That repair-deficient animals display such abnormalities underscores the fundamental importance of DNA repair in protecting against the mutagenic and cytotoxic effects of DNA damage."

[Bradford]: There is much evidence indicating that in the absence of DNA repair mechanisms genomes become corrupted in short order. This brings up a historic question. How would that first putative genome avoid the natural tendency to lose genetic information which occurs without a built in self-correction mechanism? In addition what evidence is there that a prebiotic environment would generate genetic information much less accumulation of such information at a pace that exceeds the information lost?

"Proteins participating in base excision repair (BER) cope with chromosomal damages that arise as spontaneous decomposition products or from reactions with metabolically or environmentally derived reactive chemicals (2)namely oxygen free radicals and alkylating agents."

[Bradford]: This brings up another point. Evolutionists have explained that as we look back in time to eras in which living organisms lacked biological capacities found in presently existing organisms, such organisms would have faced less competition because competing organisms also were less developed. Enhanced capacities are correlated to keener competition. However one type of challenge should have existed throughout history. Challenges to life based on environmental factors specifically, chemical reactions, should have existed at the outset as they exist today. General examples are cited by the authors. Nucleic acids are vulnerable to environmentally generated damaging reactions. Why would this not necessitate encoded self-correcting mechanisms at the origin of life? How do they fit Darwinian models?

0 Comments:

Post a Comment

Links to this post:

Create a Link

<< Home