Epistasis Blog

From the Artificial Intelligence Innovation Lab at Cedars-Sinai Medical Center (www.epistasis.org)

Wednesday, September 21, 2005

Epistasis for Fitness-Related Quantitative Traits in Arabidopsis thaliana

Russell Malmberg at the University of Georgia has published a new paper in Genetics on epistasis in Arabidopsis.

Malmberg RL, Held S, Waits A, Mauricio R. Epistasis for Fitness-Related Quantitative Traits in Arabidopsis thaliana Grown in the Field and in the Greenhouse. Genetics. 2005 Sep 12 [PubMed]


The extent to which epistasis contributes to adaptation, population differentiation, and speciation is a long-standing and important problem in evolutionary genetics. Using recombinant inbred lines of Arabidopsis thaliana grown under natural field conditions, we have examined the genetic architecture of fitness-correlated traits with respect to epistasis; we identified both single locus additive and two locus epistatic QTLs for natural variation in fruit number, germination, and seed length and width. For fruit number, we found 7 significant epistatic interactions, but only 2 additive QTLs. For seed germination, length, and width, there were from 2 to 4 additive QTLs and 5-8 epistatic interactions. The epistatic interactions were both positive and negative. In each case, the magnitude of the epistatic effects were roughly double those of the effects of the additive QTLS, varying from -41% to +29% for fruit number, and from -5% to +4% for seed germination, length, and width. A number of the QTLs we describe participate in more than one epistatic interaction, and some loci identified as additive also may participate in an epistatic interaction; the genetic architecture for fitness traits may be a network of additive and epistatic effects. We compared the map positions of the additive and epistatic QTLs for germination, seed width, and seed length from plants grown in both the field and greenhouse. While the total number of significant additive and epistatic QTLs was similar between the two growth conditions, the map locations were largely different. We found a small number of significant epistatic QTL x environment effects when we tested directly for them. Our results support the idea that epistatic interactions are an important part of natural genetic variation, and reinforce the need for caution in comparing results from greenhouse-grown and field-grown plants.


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At 5:28 AM, Blogger cylon said...

A typical dictionary definition of hypnosis states that it is: a state that resembles sleep but that is induced by suggestion. However, anyone who has tried hypnosis (and any self respecting hypnotist) will tell you that this is a very simplistic view of the subject!
A much better description comes from the Free Online Dictionary which states that hypnosis is: an artificially induced state of consciousness, characterised by heightened suggestibility and receptivity to direction. So what does this mean and how can it be used to your advantage?

Well, the subject of hypnosis has been discussed and pondered since the late 1700s. Many explanations and theories have come and gone though science, however, has yet to supply a valid and well-established definition of how it actually happens. It's fairly unlikely that the scientific community will arrive at a definitive explanation for hypnosis in the near future either, as the untapped resources of our 'mostly' uncharted mind still remain something of a mystery.
However, the general characteristics of hypnosis are well documented. It is a trance state characterized by extreme suggestibility, deep relaxation and heightened imaginative functioning. It's not really like sleep at all, because the subject is alert the whole time. It is most often compared to daydreaming, or the feeling you get when you watch a movie or read a captivating book. You are fully conscious, but you tune out most of the outside world. Your focus is concentrated intensely on the mental processes you are experiencing - if movies didn't provide such disassociation with everyday life and put a person in a very receptive state then they would not be as popular (nor would TV advertising be as effective!). Have you ever stated that a film wasn't great because you just couldn't 'get into it'???
This works very simply; while daydream or watching a movie, an imaginary world becomes almost real to you because it fully engages your emotional responses. Such mental pursuits will on most occasions cause real emotional responses such as fear, sadness or happiness (have you ever cried at a sad movie, felt excited by a future event not yet taken place or shivered at the thought of your worst fear?).
It is widely accepted that these states are all forms of self-hypnosis. If you take this view you can easily see that you go into and out of mild hypnotic states on a daily basis - when driving home from work, washing the dishes, or even listening to a boring conversation. Although these situations produce a mental state that is very receptive to suggestion the most powerful time for self-change occurs in the trance state brought on by intentional relaxation and focusing exercises. This deep hypnosis is often compared to the relaxed mental state between wakefulness and sleep.
In this mental state, people feel uninhibited and relaxed and they release all worries and doubts that normally occupy their mind. A similar experience occurs while you are daydreaming or watching the TV. You become so involved in the onscreen antics

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