ORGANIZATION OF THE CHORION GENES OF BOMBYX MORI, A MULTIGENE FAMILY. III. DETAILED MARKER COMPOSITION OF THREE GENE CLUSTERS

Marian R. Goldsmith ¹ and Eileen Clermont-Rattner ²

¹ Department of Developmental, University of California, Irvine, Irvine, California 92717
² Department of Cell Biology, University of California, Irvine, Irvine, California 92717

The chorion patterns produced by progeny from crosses that were used to define the linked gene clusters, Ch 1, Ch 2 and Ch 3 (strain C108 vs. strain Ascoli), were examined by two-dimensional gel electrophoresis (isoelectric focusing vs. SDS/urea). Approximately 60 proteins were assigned to four previously defined chorion classes, A, B, C and H_c, believed to represent the products of related genes, on the basis of size and relative cysteine content. All strain-specific markers showed co-dominance in the F₁, indicating the likelihood that they are not products of post-translational modification. Twentyseven Ascoli markers co-segregated in testcross progeny, and none of the resolved proteins showed independent assortment, confirming their linkage to chromosome 2. Two-dimensional screening of recombinants demonstrated that all three clusters contain Class A and B markers; H_c markers have been found only in Ch 1 and Ch 2; whereas, mapped C markers were confined to Ch 3. This indicates that chorion clusters are heterogeneous with respect to the markers they contain.