Answer: The correct answer is two
Hope this helps!!
Explanation:
It really depends, think of it as 2 light bulbs in each parent. if both light bulbs in both parents are switched on that means their genes that they inherited are only able to have brown eyed babies, although if just 1 of the 4 light bulbs are not on it allows the baby to have blue eyes.
A phrase to describe a negative feedback loop could be: self-regulating (though I'm not sure the exact word you're looking for).