主题：转基因玉米导致养猪场猪绝育 -- 唵啊吽

Figure 1. Alternative Splicing of Dscam Potentially Generates 38,016 Isoforms(A) Schematic representation of Dscam gene, mRNA, and protein. The Dscam protein contains both constant and variable domains. The variable domains are encoded by alternative exons. Each block of alternative exons is indicated by a different color. A transcript contains only one alternative exon from each block. The Dscam gene encodes 12 alternative exons for the N-terminal half of Ig2 (red), 48 alternative exons for the N-terminal half of Ig3 (blue), and 33 alternative exons for Ig7 (green). There are two alternative transmembrane domains (yellow).(B) Schematic representation of Dscam proteins used in this study and explanation of isoform nomenclature. Immunoglobulin domain (Ig), horseshoe; fibronectin type III repeat (FNIII), black rectangle; transmembrane domain (TM), vertical rectangle. The NH2 and COOH termini are indicated. Individual isoforms are denoted by the combination of alternative variable Ig domains. For instance, the isoform comprising Ig2 alternative 7, Ig3 alternative 27, and Ig7 alternative 25 is designated Dscam7.27.25 or simply as 7.27.25. In this study, both full-length proteins and fragments of the extracellular domain were used. Full-length Dscam proteins expressed in COS cells and transgenic flies did not contain an epitope tag. Full-length proteins expressed in Drosophila S2 cells contained an internal FLAG epitope tag in the C-terminal cytoplasmic tail (denoted by a flag icon). For simplicity, the alternative transmembrane domain used in full-length isoforms is not indicated. Purified Dscam proteins containing different regions of the extracellular domain contained either a 6xHis tag (schematic not shown) or the Fc region of human IgG at the C terminus. Fc tags contain the hinge region, which dimerizes the Dscam proteins. 6xHis tags do not dimerize the Dscam proteins.