Lecture 15 Bio325 Fall 07

Lecture 15 Bio325 Fall 07 - Conjugation continued Fig 15.14...

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1 Conjugation, continued. Fig. 15.14 Recombination can occur between the donor chromosome (brought over by the F factor) and the homologous sequences in the recipient chromosome. A + B + C + A - B - C - at least two crossovers are required for a gene from the donor to be incorporated into the recipient, because the chromosome has to remain circular. There can also be quadruple crossovers but these are much more rare. donor recipient Conjugation recombination frequencies can be used to map gene location in E. coli: example: an Hfr strain is mixed with an F- strain. The Hfr strain is arg + met + mal + The F- strain is arg - met - mal - The mal+ gene is known to be the last of the 3 genes to be transferred from this Hfr strain. It is essential that all of the cells analyzed have transferred all of the selectable markers. The mixture is first plated on minimal media containing maltose (to select for mal + ) then replica plated on maltose media lacking either methionine or arginine or both. What is the order and relative location of each gene, and what type of recombination events led to each type of exconjugant? Fig. 15.17
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2 You have an Hfr strain with the genotype: thy + his + ade + cys + amp S and an F- strain with the genotype: thy - his - ade - cys - amp R . After mixing the two strains together, you disrupt the cells with a blender at different time points and plate the cells at each time point on the media shown below. 0 rich
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This note was uploaded on 06/19/2008 for the course BIO 325 taught by Professor Saxena during the Fall '08 term at University of Texas.

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Lecture 15 Bio325 Fall 07 - Conjugation continued Fig 15.14...

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