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Tantalizing Glimpses into a Fragmented Genome

Tantalizing Glimpses into a Fragmented Genome | Papers | Scoop.it
From www.plosbiology.org - January 30, 12:30 PM

Like other ciliates, O. trifallax has two nuclei: a micronucleus, which contains its entire genome, and a macronucleus, which houses an edited version of the genetic material that's used to run the ship. What's extraordinary about O. trifallax is the degree to which its macronuclear genetic material has been rearranged. Derived afresh each generation from the micronuclear genetic material through an elaborate process that involves chopping up chromosomes, rearranging genes, deleting virtually all of the noncoding DNA, making multiple copies of the various bits, and capping them with telomeres, it ends up with tens of thousands of “nanochromosomes” that then serve as the templates for producing all the proteins that O. trifallax needs to conduct the day-to-day business of being alive.

 

Tantalizing Glimpses into a Fragmented Genome
Mary Hoff

PLoS Biol 11(1): e1001470.

http://dx.doi.org/10.1371/journal.pbio.1001470

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Adaptive Prolonged Postreproductive Life Span in Killer Whales

From www.sciencemag.org - September 17, 2012 3:25 PM

Prolonged life after reproduction is difficult to explain evolutionarily unless it arises as a physiological side effect of increased longevity or it benefits related individuals (i.e., increases inclusive fitness). There is little evidence that postreproductive life spans are adaptive in nonhuman animals. By using multigenerational records for two killer whale (Orcinus orca) populations in which females can live for decades after their final parturition, we show that postreproductive mothers increase the survival of offspring, particularly their older male offspring. This finding may explain why female killer whales have evolved the longest postreproductive life span of all nonhuman animals.

 

Adaptive Prolonged Postreproductive Life Span in Killer Whales
Emma A. Foster, et al.

Science 14 September 2012:
Vol. 337 no. 6100 p. 1313
http://dx.doi.org/10.1126/science.1224198

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Growth dynamics and the evolution of cooperation in microbial populations

From arxiv.org - March 30, 2012 2:24 PM

Microbes providing public goods are widespread in nature despite running the risk of being exploited by free-riders. However, the precise ecological factors supporting cooperation are still puzzling. Following recent experiments, we consider the role of population growth and the repetitive fragmentation of populations into new colonies mimicking simple microbial life-cycles. Individual-based modeling reveals that demographic fluctuations, which lead to a large variance in the composition of colonies, promote cooperation. Biased by population dynamics these fluctuations result in two qualitatively distinct regimes of robust cooperation under repetitive fragmentation into groups. First, if the level of cooperation exceeds a threshold, cooperators will take over the whole population. Second, cooperators can also emerge from a single mutant leading to a robust coexistence between cooperators and free-riders. We find frequency and size of population bottlenecks, and growth dynamics to be the major ecological factors determining the regimes and thereby the evolutionary pathway towards cooperation.

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Emergent Criticality through Adaptive Information Processing in Boolean Networks

Emergent Criticality through Adaptive Information Processing in Boolean Networks | Papers | Scoop.it
From prl.aps.org - March 23, 2012 7:17 PM

We study information processing in populations of Boolean networks with evolving connectivity and systematically explore the interplay between the learning capability, robustness, the network topology, and the task complexity. We solve a long-standing open question and find computationally that, for large system sizes N, adaptive information processing drives the networks to a critical connectivity Kc=2. For finite size networks, the connectivity approaches the critical value with a power law of the system size N. We show that network learning and generalization are optimized near criticality, given that the task complexity and the amount of information provided surpass threshold values. Both random and evolved networks exhibit maximal topological diversity near Kc. We hypothesize that this diversity supports efficient exploration and robustness of solutions. Also reflected in our observation is that the variance of the fitness values is maximal in critical network populations. Finally, we discuss implications of our results for determining the optimal topology of adaptive dynamical networks that solve computational tasks.

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Why Millennials Don't Want To Buy Stuff

Why Millennials Don't Want To Buy Stuff | Papers | Scoop.it
From www.fastcompany.com - July 17, 2012 2:04 PM

Compared to previous generations, Millennials seem to have some very different habits that have taken both established companies and small businesses by surprise. One of these is that Generation Y doesn't seem to enjoy purchasing things.


The Atlantic's article "Why Don't Young Americans Buy Cars?" mused recently about Millennials' tendency to not care about owning a vehicle. The subtitle: "Is this a generational shift, or just a lousy economy at work?"


What if it's not an "age thing" at all? What's really causing this strange new behavior (or rather, lack of behavior)? Generational segments have profound impacts on perception and behavior, but an "ownership shift" isn't isolated within the Millennial camp. A writer for USA Today shows that all ages are in on this trend, but instead of an age group, he blames the change on the cloud, the heavenly home our entertainment goes to when current media models die. As all forms of media make their journey into a digital, de-corporeal space, research shows that people are beginning to actually prefer this disconnected reality to owning a physical product.


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Strong gender differences in reproductive success variance, and the times to the most recent common ancestors

From arxiv.org - March 30, 2012 2:23 PM

The Time To the Most Recent Common Ancestor (TMRCA) based on human
mitochondrial DNA (mtDNA) is estimated to be twice that based on the
non-recombining part of the Y chromosome (NRY). These TMRCAs have special
demographic implications because mtDNA is transmitted only from mother to
child, and NRY from father to son. Therefore, mtDNA reflects female history,
and NRY, male history. To investigate what caused the two-to-one female-male
TMRCA ratio in humans, we develop a forward-looking agent-based model (ABM)
with overlapping generations and individual life cycles.

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