In the following illustration, the upper line shows a gene composed of segments A€“D. The lower circle shows a mutant version of this gene, consisting of two fused pieces (A-B, C-D), carried on a plasmid. You attempt a targeted mutagenesis of a diploid cell by transforming cells with the cloned mutant gene. The following diagram shows the desired pairing of the plasmid and chromosome just prior to recombination.

You prepare DNA from the cells, digest it with an enzyme that cuts at x, and hybridize the cleaved DNA with the probe shown above. The following diagram shows a Southern blot of possible results.

(a) Which lane shows fragments produced from DNA in the cell before transformation? 

(b) Which lane shows fragments produced from DNA in the cell in which the anticipated targeted mutagenesis occurred?
(c) Which of these blot patterns might be expected if two crossovers occurred, one between A and B, and the other between C and D?

Transcribed Image Text:

Probe A I D" х B' C х A" Plasmid 2 4 5