In eukaryotes, one of the complexities of post-transcriptional processing of RNA is that alternative splicing can occur. A pre-mRNA transcribed from one gene can lead to different final mRNA molecules, and, subsequently translated into different proteins. The different variations of fibronectin, an adhesive cell surface protein, serve as an example of related proteins generated by different patterns of splicing of a single RNA transcript. As another example, whether an antibody will be retained on the cell surface or secreted depends on differences in splicing the primary RNA transcript.