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Lambda study question

Study question

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#1 JellowK



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Posted 18 April 2012 - 06:17 AM

Hey I have a study question I really need help with

If a lambda lysogen is induced with ultraviolet light, a lysate results in which about one clear-plaque mutant per 10^4
phage is present. If a culture of a lysogen is grown without any prior induction and the culture fluid is
analyzed for-free phage that are spontaneously released, the fraction that form clear plaques is always
higher than what induction gives.

(a) Explain the higher frequency of clear-plaque mutants among the spontaneously released phage.

This question is very problematic since ive seen that induction to the cell usually gives higher frequency of
clear plaques then normal growth would and thereby spontaneously give rise to lytic pathway that end up clear plaque.

could someone explain to me how this statement work?

( b Among the spontaneously released phage in which of the genes cI, cll, or cIII do you suppose the
mutations reside that yield a clear plaque?

This should be cI gene since that is actually the maintance gene for the actually expression of repression of lytic pathway when
the cell is a lysogen. Inactivation of cII and cIII by a mutation should not give any clear-plaque since they are only needed
at the ination of lysogenisation

Also is there some method one could use to actually prove that cI is the actuall one thats needed to be mutated to
get clear - plaque?


Edited by JellowK, 18 April 2012 - 06:18 AM.

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