17.But the exact nitty gritty origins of mutations and variations in biology are still uncertain. 但是,生物界的突变和变异起源的准确的事实真相仍不确定. 18.Alright , so what is the nitty gritty on coat color inheritance? 是什么决定了拉拉的颜色? 19.Let's get down to the nitty-gritty. nitty...