Which type of chromosome alteration results in the formation of a tetravalent (cross-like) structure at synapsis?

The type of chromosome alteration that results in the formation of a tetravalent (cross-like) structure at synapsis is the reciprocal translocation. It is typically an exchange of genetic material of nonhomologous chromosomes. It happens in about 1 for every 500 newborns. 

Cheek cells are animal eukaryotic cells, while tomato, potato and onion cells are eukaryotic plant cells.

So, to know the difference between them, it is enough to compare between an animal and vegetal cell.

The plant cells and animal cells can be differentiated by their shape and their organelles.

Both are eukaryotes, but the presence of components like the chloroplasts, cell wall, and vacuoles are specific of plant cells and absent in animal cells.

The size of the plant cells are larger and the shape more regular than the animal cell.