Transduction     is     genetic
   recombination mediated by phages.
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   A phage infects a "donor" bacterium.
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   In  its  lytic cycle, the phage accidentally packages some "donor" DNA
   (e.g. A^+ allele) in its protein coat.
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   When  progeny  phage  then  infect  a  "recipient"  cell, DNA from the
   "recipient" may exchange with that of the "donor".
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   The "recipient" becomes a recombinant (A^+ B^-).