Molecular Genetics

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Homologous (or general) recombination is at the heart of genetics.

• It is the basis for the construction of genetic maps.
• Understanding of the mechanisms of homologous recombination has thus been widely sought after.
• Understanding has been approached with each the genetic, morphological and molecular chromosomes.

Homologous recombination is distinguished from other types of recombination:

• Site-specific recombination, as exemplified by invertible elements, resolvases, and some phage DNA integration events are examples of non-homologous recombination. Though in many cases identical sequences are required at the two recombining sites, the sequences are short, distinguishing them from the longer stretches (hundreds of bp) used in homologous recombination.
• Transposition is another example of non-homologous recombination. Usually the target site bears no sequence relationship to the ends of the transposable element.
• Random integration of transforming DNA during genetic engineering is a non-homologous recombination event, but directed integration as used in creating gene knock-outs, is homologous recombination.
• Chromosome deletions, inversions and translocations are often considered the result of non-homologous recombination, though often they occur at regions of considerable sequence similarity. They may thus be considered as results of aberrant homologous recombination. This may be thought of as homologous recombination at non-homologous positions.

This is page 35 of Molecular Genetics by Ulrich Melcher, © 1997, 1998