| Description |
The nature of chromosome pairing initiation is currently poorly understood. Three models have been proposed in the literature to describe how pairing is initiated. The first model states that pairing is initiated at the centromere and/or telomeres and then proceeds through processional pairing. The second model states that pairing is initiated at specific internal sites along the chromosome. The third model states that chromosomes move through the nucleus randomly by a type of Brownian motion and when large regions of homology come into contact, they pair. To test these three models, we have designed an experiment using the FLP-FT site-specific recombinase system to produce a series of inversions that vary in size and location in Drosophila melanogaster and then reverted these inversions. An inverted chromosome attempts to pair with its normal homologue via the formation of an inversion loop. The formation of an inversion loop influences the rate of reversion since it brings the FRTs in close proximity. Thus, the ability ot revert indicates how well the homologous chromosomes are able to pair. Our experimental data support the second hypothesis because the formation of the inversion loop will be influenced by the location of the pairing sites relative to the inversion. |
