The smallest and most exclusive grouping category is species.
The answer is language. Humans have a high degree of language acquisition and complexity compared to
chimpanzees due to foxp2 proteins. Foxp2
are transcription factors that are significant in cell proliferation. The difference of 2 in 700 amino acids in the sequence makes the protein to be differentially regulated between the two
species.
If mitosis occurred without cytokinesis, the cell would contain two nuclei and twice the DNA. If cytokinesis occurred without mitosis , one of the new cells would lack DNA and a nucleus altogether. The cell cycle is regulated by signals both inside and outside of the cell.