Re: two tone iris odds

That is dependent on several factors: the exact nature of the inheritence 
of such a characteristic (dependent on 1 gene or polygenetic), and the 
reletive frequency in the population.  When Gregor Mendel investigated 
peas, he believed that short vs. tall should break out 25 % short, 50 % 
medium, 25 % tall.  If one of the features is dominant, then it would be 
25 % short, 75 % tall.  These breakdowns assume that short and tall genes 
are equally distributed in the population.  If short genes are more 
prevalent than tall, more complex things happen.

Pursue this interest.  There will be much research in this over the next 10 
years.