Cornell Conference Informatics Natural selection

Open Mike: Cornell OBI Conference Chapter 12—“Can Purifying Natural Selection Preserve Biological Information?”—Abstract

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Biological Information

To facilitate discussion, we are publishing the abstracts and conclusions/summaries/Introduction excerpts of the 24 papers from the Cornell Conference on the Origin of Biological Information here at Uncommon Descent, with cumulative links to previous papers at the bottom of each page. You can get from anywhere to anywhere in the system.

Note: A blow-by-blow account of the difficulties that the authors experienced from Darwin lobby attempts to censor the book by denying it publication with Springer are detailed here. Fortunately, the uproar resulted in an opportunity for readers like yourself to read the book online. That said, the hard cover version is now shipping.

The Abstract for “Can Purifying Natural Selection Preserve Biological Information?” by Paul Gibson, John R. Baumgardner, Wesley H. Brewer, John C. Sanford:

Most deleterious mutations have very slight effects on total fitness, and it has become clear that below a certain fitness effect threshold, such low-impact mutations fail to respond to natural selection. The existence of such a selection threshold suggests that many low-impact deleterious mutations should accumulate continuously, resulting in relentless erosion of genetic information. In this paper, we use numerical simulation to examine this problem of selection threshold.

The objective of this research was to investigate the effect of various biological factors individually and jointly on mutation accumulation in a model human population. For this purpose, we used a recently-developed, biologically-realistic numerical simulation program, Mendel’s Accountant. This program introduces new mutations into the population every generation and tracks each mutation through the processes of recombination, gamete formation, mating, and transmission to the new offspring. This method tracks which individuals survive to reproduce after selection, and records the transmission of each surviving mutation every generation. This allows a detailed mechanistic accounting of each mutation that enters and leaves the population over the course of many generations. We term this type of analysis genetic accounting.

Across all reasonable parameters settings, we observed that high impact mutations were selected away with very high efficiency, while very low impact mutations accumulated just as if there was no selection operating. There was always a large transitional zone, wherein mutations with intermediate fitness effects accumulated continuously, but at a lower rate than would occur in the absence of selection. To characterize the accumulation of mutations of different fitness effect we developed a new statistic, selection threshold (STd), which is an empirically determined value for a given population. A population’s selection threshold is defined as that fitness effect wherein deleterious mutations are accumulating at exactly half the rate expected in the absence of selection. This threshold is mid-way between entirely selectable, and entirely unselectable, mutation effects.

Our investigations reveal that under a very wide range of parameter values, selection thresholds for deleterious mutations are surprisingly high. Our analyses of the selection threshold problem indicate that given even modest levels of noise affecting either the genotype-phenotype relationship or the genotypic fitness-survival-reproduction relationship, accumulation of low-impact mutations continually degrades fitness, and this degradation is far more serious than has been previously acknowledged. Simulations based on recently published values for mutation rate and effect-distribution in humans show a steady decline in fitness that is not even halted by extremely intense selection pressure (12 offspring per female, 10 selectively removed). Indeed, we find that under most realistic circumstances, the large majority of harmful mutations are essentially unaffected by natural selection and continue to accumulate unhindered. This finding has major theoretical implications and raises the question, “What mechanism can preserve the many low-impact nucleotide positions that constitute most of the information within a genome?” More.

See also: Origin of Biological Information conference: Its goals

Open Mike: Origin of Biological Information conference: Origin of life studies flatlined

Open Mike: Cornell OBI Conference— Can you answer these conundrums about information?

Open Mike: Cornell OBI Conference—Is a new definition of information needed for biology? (Chapter 2)

Open Mike: Cornell OBI Conference—New definition of information proposed: Universal Information (Chapter 2)

Open Mike: Cornell OBI Conference—Chapter Three, Dembski, Ewert, and Marks on the true cost of a successful search

Open Mike: Cornell OBI Conference—Chapter Three on the true cost of a successful search—Conservation of information

Open Mike: Cornell OBI Conference—Chapter Four: Pragmatic Information

Open Mike: Cornell OBI Conference—Chapter Four, Pragmatic information: Conclusion

Open Mike: Cornell OBI Conference Chapter Five Abstract

Open Mike: Cornell OBI Conference Chapter Five – Basener on limits of chaos – Conclusion

Open Mike: Cornell OBI Conference Chapter Six – Ewert et all on the Tierra evolution program – Abstract

Open Mike: Cornell OBI Conference Chapter Six – Ewert et all on the Tierra evolution program – Conclusion

Open Mike: Cornell OBI Conference Chapter 7—Probability of Beneficial Mutation— Abstract

Open Mike: Cornell OBI Conference Chapter 7—Probability of Beneficial Mutation— Conclusion

Open Mike: Cornell OBI Conference Chapter 8—Entropy, Evolution and Open Systems—Abstract

Open Mike: Cornell OBI Conference Chapter 8—Entropy, Evolution and Open Systems—Conclusion

Open Mike: Cornell OBI Conference Chapter 9—Information and Thermodynamics in Living Systems—Abstract

Open Mike: Cornell OBI Conference Chapter 9—Information and Thermodynamics in Living Systems—Conclusion

Open Mike: Cornell OBI Conference Chapter 10—Biological Information and Genetic Theory: Introductory Comments—Abstract

Open Mike: Cornell OBI Conference Chapter 10—Biological Information and Genetic Theory: Introductory Comments— Excerpt

Open Mike: Cornell OBI Conference Chapter 11—Not Junk After All—Abstract

Open Mike: Cornell OBI Conference Chapter 11—Not Junk After All—Conclusion

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