I see so-called 'pure' traits advertised as being worth more on the secondary market. A sierra from two sierra parents and all sierra grandparents.

I can see that IF you just want a series of Sierra that this might have some value.

However if a trait is made up of a number of alleles then doesn't breeded a 'pure' trait pretty much eliminate alleles that might be combined later for more rare traits?

Doesn't 'purity' limit the following generations evolution?