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Letter from Gordon Allen to Joshua Lederberg

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  • Biology


155 Corona Ave Pelham 65, N. Y. Friday, April 14 Dear Joshua: You have prsbably been rather eager to EX& hear my further comments about pleiotropy, and I'm sorry that this is the first chance I've had to sit down and write to you. The secondary fermentation affects I mentioned in my last letter were in our own mutant strains: tryptophaneless was lac-, mal- (plus-minus on second day); histidineless was mal', mannitol and galactose slow plus-minus; another with unidentified require- ments was xylose plus-minus, and a cyst&neless *h appeared to be negative for all fermentations until we found that its metabolism was somehow interfered with by the EM3 medium.(we never solved it comtiletely). Some were, unfortunately, already lac', and we didn't test on other sugars at that time because plates weren't madeup. Your evidence against pleiotrops## is convincing in the case of maltose, and if maltose can behgBe that way, so can the other sugars. The pleiotrop$fi$ idea would have explained most of the aberrEtnt behavior of sugarxx markers insofar as there &as an excess of matives, because there might have been two or more mutations which singly, or in combination with other mutations, could prevent & mfermentationl. The great excess of negatives among all my recombinants would 22% be nicely explaIned by this, and it would seem also to account for the prrm@llrnrjt segregation bias you told me of this summer. segregation" It could account for some degree of "partial because a ILac v Mal- might be segregating for two different Kal- mutations. To account for more than 759 of Mal- you'd have to assume 3 or more loci, or else postulate some sort of repulsion between ttle two ImzAtu mutations. If Lac v Hal+-* w r t'hough, pleiotropy could not explain it. Bernie's suggestion of physiological side-effects is also I think.. He %ompares it w:th the mucoid charac- and among some He thinks the mucoid trait state that can be acU.&ed by many dif- both g

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