Problem:

This is reference to a review on C. elegans mosaic analysis by Yochem and Herman, in which the authors make a distinction between free chromosome fragments and extrachromosomal arrays.

For the former, they reference Herman 1984. For the latter, they reference Lackner et al 1994 and Miller et al 1996, but these are studies that use extrachromosomal arrays, not papers defining them as a technique, per se.

I am curious to know what the distinction is - I am under the impression that extrachromosomal arrays are fragments with many copies of the gene of interest + a marker.