With a growing American law enforcement presence on the border, illegal crossings have become so difficult -- and even deadly -- that many migrants and their families choose to stay in the United States, rather than to risk a repeated crossing, migration experts say.
If QTL clusters contain tightly linked but distinct genes, as in these examples, the problem of linkage drag can be overcome by repeated crossing and careful marker-assisted selection to break the linkage between desirable and undesirable genes and to select the ideal combination of alleles.
This is suggestive of a hybridisation event between the two species, with the genomic background of the grey having been diluted out through repeated crossing with red jungle fowl.
Their original material had flower longevity of 5.7 days, but through repeated crossing, the sixth generation had increased its mean of flower life to 15.9 days.
The p5cr-1 mutant line originally contained at least one additional T-DNA insertion that was eliminated by repeated crossing to the Col-8 wildtype.
DOI: http://dx.doi.org/10.7554/eLife.09224.005 Note that in rare instances (1 out of 32 molecules, Table 1), SpoIIIE managed to traverse the 30-bp dsMeP insert, albeit after several seconds of repeated crossing attempts.
