Events duplicating

Phase and antigenic variation in bacteria. These may be mediated by slipped-strand mispairing of repeat sequences that occur in these phase variable genes or by gene duplication events. 

The evolutionary hypothesis is that the ancestral molecule of apo(a) was a plasminogen-type protein, having five kringles, that emerged by a duplication event from a protein with one kringle and one serine protease domain about 300 million years ago (12). 

If two events are NOT mutually exclusive, you must add the probabilities of the events and then subtract out the duplicate events. 

Bowers JE, Chapman BA, Rong J, Paterson AH (2003) Unraveling angiosperm genome evolution by phylogenetic analysis of chromosomal duplication events. Nature 422 433 38... 

The three molecules of the IL-1 family, interleukin-la (IL-la), interleukin-1 3 (IL-ip), and interleukin-1 receptor antagonist (IL-IRa) map to the long arm of chromosome two in the human genome. It appears that the family arose via a gene duplication event some 350 million years ago, and the molecules possess between 27.5 and 36% sequence identity with each other (Table 2) [1,14,15]. In addition, the genes for the two IL-1 receptors IL-1R1 and IL-1RII [16,17], and an IL-1R accessory protein (IL-lRacP), which binds to the IL-1, IL-1 receptor complex [18], have been identified. Together, these molecules via their differential activity serve primarily to modulate the host defense mechanism. 

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