Complex Genes - Immunoglobulin gene, dimorphic and cryptomorphic genes are grouped as complex genes.

These genes do not have defined exon or intron sequences, the exon in one instance might be intron in another case.

A single complex gene may code for many types of proteins each with affinity to different proteins or function.

These genes show excessive rearrangement in sequence (mRNA), i.e., before post transcriptional modifications.

For example, immunoglobulin mRNA is cleaved through a series of steps before it is translated.