Kevin Cook at the Bloomington Stock Center has been funded by the National Center for Research Resources to generate chromosomal duplication coverage for the X chromosome. The goals of the project are to create large duplications which will provide maximal coverage and will subdivide the X chromosome with closely spaced breakpoints. A list of the duplications we have generated is provided at Bloomington X chromosome duplications.
To isolate Dp(1;Y) chromosomes, we generated attached-XY chromosomes with inversions in the X chromosome. The inversions have one breakpoint near the tip of the X and another breakpoint in the medial part of the X. When these “inversion + attached-XY” chromosomes are irradiated, Dp(1;Y) chromosomes can be isolated from large internal deletions.
Each irradiation screen with a particular inversion gives rise to a set of Dp(1;Y) chromosomes in which the medial segments share a common proximal end (on the standard map) yet have different distal ends. When inversions with different proximal breakpoints are irradiated, multiple sets of nested duplicated medial segments can be isolated.
A common distal segment including the yellow gene is shared by all duplications (shown above as the grayed area of X euchromatin).
The proximal X chromosome segment is usually wholly heterochromatic, but may occasionally contain genes from basal euchromatin (polytene division 20).
For more information, see Constructing duplication progenitor chromosomes, Mapping duplication breakpoints and Genetic background of the Bloomington duplications.
R. Kimberley Cook, Megan E. Deal, Jennifer A. Deal, Russell D. Garton, C. Adam Brown, Megan E. Ward, Rachel S. Andrade, Eric P. Spana, Thomas C. Kaufman and Kevin R. Cook (2010) "A New Resource for Characterizing X-Linked Genes in Drosophila melanogaster: Systematic Coverage and Subdivision of the X Chromosome With Nested, Y-Linked Duplications" Genetics 186: 1095 - 1109.