Is Evolution Predictable?

Started by stromboli, February 21, 2013, 09:26:17 AM

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stromboli

this:
http://www.dailygalaxy.com/my_weblog/20 ... tions.html
QuoteUnderstanding how and why diversification occurs is important for understanding why there are so many species on Earth. In a new study published on 19 February in the open access journal PLOS Biology, researchers show that similar—or even identical—mutations can occur during diversification in completely separate populations of E. coli evolving in different environments over more than 1000 generations. Evolution, therefore, can be surprisingly predictable.

The experiment, conducted by Matthew Herron, research assistant professor at the University of Montana, and Professor Michael Doebeli of the University of British Columbia, involved 3 different populations of bacteria. At the start of the experiment, each population consisted of generalists competing for two different sources of dietary carbon (glucose and acetate), but after 1200 generations they had evolved into two coexisting types each with a specialized physiology adapted to one of the carbon sources. Herron and Doebeli were able to sequence the genomes of populations of bacteria frozen at 16 different points during their evolution, and discovered a surprising amount of similarity in their evolution.
"In all three populations it seems to be more or less the same core set of genes that are causing the two phenotypes that we see," Herron said. "In a few cases, it's even the exact same genetic change." Recent advances in sequencing technology allowed Herron and Doebeli to sequence large numbers of whole bacterial genomes and provide evidence that there is predictability in evolutionary diversity. Any evolutionary process is some combination of predictable and unpredictable processes with random mutations, but seeing the same genetic changes in different populations showed that selection can be deterministic.

"There are about 4.5 million nucleotides in the E. coli genome," he said. "Finding in four cases that the exact same change had happened independently in different populations was intriguing." Herron and Doebeli argue that a particular form of selection—negative frequency dependence—plays an important role in driving diversification. When bacteria are either glucose specialists or acetate specialists, a higher density of one type will mean fewer resources for that type, so bacteria specializing on the alternative resource will be at an advantage.

Quote"We think it's likely that some kind of negative frequency dependence—some kind of rare type advantage—is important in many cases of diversification, especially when there's no geographic isolation," Herron said. As technology advances, Herron believes that similar experiments in larger organisms will soon be possible. Some examples of diversification without geographic isolation are known in plants and animals, but it remains to be seen whether or not the underlying evolutionary processes are similar to those in bacteria.

The second quote to me is the question- given that we see similar development in E Coli over time, with different environments, where then do we encounter diversity? In the case of E Coli, we are talking a very short lifespan. In larger organisms with longer age and even wider spread- with rats, for example- what are the factors that drive diversity?
Any geneticists on here I'd love some input.

bennyboy

I'm not a geneticist, but I don't find this result all that surprising.  Given that a phenotype must be represented at the genetic level, and that in a strongly-controlled environment, the same phenotype may provide a statistical advantage every time, especially in simpler organisms.  I'm curious-- when you say "different environments," do you just mean they were isolated from each other, or were they different in composition?

Also, go UBC!  (my alma mater)
Insanity is the only sensible response to the universe.  The sane are just making stuff up.

Alaric I

It may not be predictable now, but I think we will soon not only be able to predict it, but to control it!!

Why do I say this?  Easy, We have figured out how DNA is contructed (not completely but) enough to store data on DNA strands!!

http://www.sciencefriday.com/segment/01 ... n-dna.html

If they can watch changes in the DNA and unlock the mytery of what configurations do, we could arguably change that to eraticate things such as AIDS and Down Syndrome. (I pick these because they are two negative effect of evolution.)

Icarus

Quote from: "bennyboy"I'm not a geneticist, but I don't find this result all that surprising.  Given that a phenotype must be represented at the genetic level, and that in a strongly-controlled environment, the same phenotype may provide a statistical advantage every time, especially in simpler organisms.  I'm curious-- when you say "different environments," do you just mean they were isolated from each other, or were they different in composition?

Also, go UBC!  (my alma mater)

Not necessarily, the colour of a siamese cats coat is dependent on the temperature it was raised in. The same genotype produces different phenotypes based solely on the environment.

"The pointed pattern [1] is a form of partial albinism, resulting from a mutation in tyrosinase, an enzyme involved in melanin production. The mutated enzyme is heat-sensitive; it fails to work at normal body temperatures, but becomes active in cooler areas of the skin.[11] This results in dark colouration in the coolest parts of the cat's body, including the extremities and the face, which is cooled by the passage of air through the sinuses. All Siamese kittens, although pure cream or white at birth, develop visible points in the first few months of life in colder parts of their body."

It is also possible to have different genotypes producing the same phenotype, there are many cases when you have two or more genes contributing to a phenotype so you can have different combinations of genotypes for the one phenotype.

bennyboy

Quote from: "Icarus"
Quote from: "bennyboy"I'm not a geneticist, but I don't find this result all that surprising.  Given that a phenotype must be represented at the genetic level, and that in a strongly-controlled environment, the same phenotype may provide a statistical advantage every time, especially in simpler organisms.  I'm curious-- when you say "different environments," do you just mean they were isolated from each other, or were they different in composition?

Also, go UBC!  (my alma mater)

Not necessarily, the colour of a siamese cats coat is dependent on the temperature it was raised in. The same genotype produces different phenotypes based solely on the environment.

"The pointed pattern [1] is a form of partial albinism, resulting from a mutation in tyrosinase, an enzyme involved in melanin production. The mutated enzyme is heat-sensitive; it fails to work at normal body temperatures, but becomes active in cooler areas of the skin.[11] This results in dark colouration in the coolest parts of the cat's body, including the extremities and the face, which is cooled by the passage of air through the sinuses. All Siamese kittens, although pure cream or white at birth, develop visible points in the first few months of life in colder parts of their body."

It is also possible to have different genotypes producing the same phenotype, there are many cases when you have two or more genes contributing to a phenotype so you can have different combinations of genotypes for the one phenotype.
For sure.  Another example I've heard is that sexual the development of some gender characteristics is very sensitive to the environment as early as the womb.
Insanity is the only sensible response to the universe.  The sane are just making stuff up.

Jason78

QuoteIs Evolution Predictable?

Only if you're really really into statistics and markov chains :D
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