Nothing... it means nothing and your inability to define it precisely beyond vague concepts proves it.

Races have a precise meaning in domestic animal breeding, there is a rule book, you cull the offspring that mutates too far away and aim at purity of attributes as defined in the standard. You get certification for your animals by various standard association who measure shape, color and size.

It makes no sense for humans. You can say gene X produce problem Y if you want, but there s no discrete segmentation in humans.