Human traits controlled by multiple alleles are called multiple-allele traits. One widely known example is ABO blood type, which is controlled by 3 alleles.
Yes, they can benefit an organism. That is why evolution works
<span>The correct answer would be amoeba. So the amoeba consists of protoplasm and a nucleus. For an amoeba the nucleus is a major organelle, which is located centrally. As such a major organelle it naturally has a huge role, and that is that it controls reproduction (it contains the chromosomes) and many other important functions (including eating and growth).</span>