Figure 7.

Proposed model of spiggin gene amplification by L1 retrotransposon‐mediated unequal crossing over, gene conversion and retrotransposition. Boxes 1 and 2 show how insertion of L1 retrotransposons on either side of the ancestral single‐copy MUC19 may have been responsible for the initial gene duplication through unequal crossing over. Box 3 indicates how further gene duplication and divergence could have led to the three major spiggin gene lineages, A, B and C. Box 4 indicates how retrotransposition has led to further gene duplication.