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Talk:Flaws in Richard Lenski Study (view source)
Revision as of 17:45, July 14, 2008
, 17:45, July 14, 2008→Richard Lenski incorrectly included generations of the E. coli already known to contain Cit+ variants in his experiments.[3] Once these generations are removed from the analysis, the data disprove Len
: Your explanation is not convincing. Show us how Lenski proved that the samples did not have '''any''' Cit<sup>+</sup> variants, if you really think he's claiming that.--[[User:Aschlafly|Aschlafly]] 20:51, 13 July 2008 (EDT)
: Your explanation is not convincing. Show us how Lenski proved that the samples did not have '''any''' Cit<sup>+</sup> variants, if you really think he's claiming that.--[[User:Aschlafly|Aschlafly]] 20:51, 13 July 2008 (EDT)
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How did Lenski obtain Cit- clones from later populations after Cit+ had become the dominant phenotype? It's pretty standard procedure. First, keep in mind that these populations contained a minority of Cit- cells. Now, a small liquid growth is made from the frozen glycerol stock of cells from a given generation, say 32,000. This is grown to an appropriate OD and then plated on a standard rich media agar plate. Provided that the plated sample isn't too dense, this plating will deposit somewhere between 15-100 individual cells on the agar, with plenty of spacing between them. The plate is then incubated at 37 C for a given time, during which the individual cells replicate to form small, visible colonies. These colonies will consist solely of cells that are genetically identical to the original cell deposited on the agar. This is all well and good, but how do you find which of the colonies are Cit-? Here you use a technique called replica plating. The agar plate is gently inverted onto a sterile swatch of velvet so that some of the cells from each colony are deposited onto the fabric. Next, a citrate-only agar plate is pressed against the velvet, transferring cells from the fabric to the new plate in exactly the same spacial orientation as the first plate. The cells are then allowed to grow on the citrate-only plate. When we then compare the two plates, we look for colonies on the rich plate that did not grown on the citrate-only plate. These colonies will be Cit-, and can be used for the replay experiments. [[User:Gerlach|Gerlach]] 13:45, 14 July 2008 (EDT)
== 1. Lenski's "historical contingency" hypothesis, as specifically depicted in Figure 3, is contradicted by the data presented... ==
== 1. Lenski's "historical contingency" hypothesis, as specifically depicted in Figure 3, is contradicted by the data presented... ==