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New findings re the mechanism of genetic change?


In water fleas, from ScienceDaily:

Current theory says similar conditions will favor phenotype changes within and across generations of organisms. Walsh’s experiment, which involved about 25 lineages of Daphnia, contradicts that thought.

“The surprising aspect of our research is, they couldn’t do both,” said Walsh, who is lead author on a paper published in Proceedings of the Royal Society B. “They could either do something that strengthens their own fitness and their own survival or they could do something to strengthen the fitness and survival of future generations. What we’re trying to find now is what makes these responses happen.”

“Dr. Walsh’s research suggests that environmental cues experienced by one generation can affect growth and maturation of future generations in ways that are not explained by current theory,” she said. “This elegant study highlights the need for the use of similar experiments to test important biological theories with direct implications for how organisms are affected by changes in their environment.”

Here’s the abstract:

Much work has shown that the environment can induce non-genetic changes in phenotype that span multiple generations. Theory predicts that predictable environmental variation selects for both increased within- and across-generation responses. Yet, to the best of our knowledge, there are no empirical tests of this prediction. We explored the relationship between within- versus across-generation plasticity by evaluating the influence of predator cues on the life-history traits of Daphnia ambigua. We measured the duration of predator-induced transgenerational effects, determined when transgenerational responses are induced, and quantified the cues that activate transgenerational plasticity. We show that predator exposure during embryonic development causes earlier maturation and increased reproductive output. Such effects are detectable two generations removed from predator exposure and are similar in magnitude in response to exposure to cues emitted by injured conspecifics. Moreover, all experimental contexts and traits yielded a negative correlation between within- versus across-generation responses. That is, responses to predator cues within- and across-generations were opposite in sign and magnitude. Although many models address transgenerational plasticity, none of them explain this apparent negative relationship between within- and across-generation plasticities. Our results highlight the need to refine the theory of transgenerational plasticity. (paywall)

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*********************************************************** *********************************************************** *********************************************************** Very interesting summary written by gpuccio:
Indeed, what we see in research about cell differentiation and epigenomics is a growing mass of detailed knowledge (and believe me, it is really huge and daily growing) which seems to explain almost nothing. What is really difficult to catch is how all that complexity is controlled. Please note, at this level there is almost no discussion about how the complexity arose: we have really non idea of how it is implemented, and therefore any discussion about its origin is almost impossible. Now, there must be information which controls the flux. It is a fact that cellular differentiation happens, that it happens with very good order and in different ways in different species, different tissues, and so on. That cannot happen without a source of information. And yet, the only information that we understand clearly is then protein sequence information. Even the regulation of protein transcription at the level of promoters and enhancers by the transcription factor network is of astounding complexity. Please, look at this paper: Uncovering Enhancer Functions Using the ?-Globin Locus. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4199490/pdf/pgen.1004668.pdf In particular Fig. 2. And this is only to regulate the synthesis of alpha globin in red cells, a very straightforward differentiation task. So, I see that, say, 15 TFs are implied in regulating the synthesis of one protein, I want to know why, and what controls the 15 TFs, and what information guides that control. My general idea is that, unless we find some completely new model, information that guides a complex process, like differentiation, in a reliable, repetitive way must be written, in some way, somewhere. That’s what I want to know: where that information is written, how it is written, how does it work, and, last but not least, how did it originate? — gpuccio
*********************************************************** *********************************************************** *********************************************************** Dionisio
Innovative, Creative, Purposeful, and far reaching effects. High School Textbook Darwinism gives us squat as tools to understand true Bio Reality. "Oh, but the "fittest" survived". Tautological Squat lessons for the High Schoolers. ppolish
as to: "Walsh and his co-authors found that these threats could lead to changes in development rates of the Daphnia that could last for two generations. Their results also consistently showed that a negative relationship existed between within generation alterations of development and trans-generational changes. In other words, the more changes within a generation almost always correlated with less change from the norm in the next generation." So it seems, contrary to what Darwinism would predict, there is in-built limits to phenotypic plasticity. bornagain77

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