Figure 7

An 8-event model for the duplication and deletion history of the human A3 repertoire. Z1, Z2 and Z3 domains are colored green, orange and blue, respectively. Five duplication and three deletion events were predicted to transform the ancestral locus into the present-day human A3 repertoire. The first event was predicted to occur between two copies of the ancestral Z1-Z2-Z3 locus. The Z domain(s) affected by each unequal crossing-over (UCO) event is shaded gray. The crossing-over points are indicated by a dashed line arrows, and the resulting Z domain configurations are shown (we assumed that new configurations achieved homozygosity prior to being involved in a subsequent UCO). Although deletion events 3 and 4 are illustrated as interchromosomal UCOs, they could have also been caused by intrachromosomal events. Event 4 is depicted before an inferred 'intermediate ancestor' common to nearly all of our models and therefore considered parsimonious, but this event could have occurred any time after event 2. The underlying phylogeny for this model is identical to that shown in Figure 1, except the N-terminal domain of human A3B diverged prior to the point at which the N-terminal domains of human A3F/A3DE and A3G split. An alternative depiction of this model is shown in Additional File 7 and details can be found in the main text and Methods.