Choose the best description for prokaryotic cell. has a nucleus; found in multicellular organisms has no nucleus; found in unicellular organisms has no nucleus; found in multicellular organisms has a nucleus; found in unicellular organisms

Prokaryotes are unicellular organisms that lack organelles or other internal membrane-bound structures. Therefore, they do not have a nucleus, but, instead, generally have a single chromosome: a piece of circular, double-stranded DNA located in an area of the cell called the nucleoid.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).