Centricles play specific roles during the division of

Centrioles play a notable role in cell division. ... These spindle fibers act as guides for the alignment of the chromosomes as they separate later during the process of cell division. Though centrioles play a role in the mitosis of animal cells, plant cells are able to reproduce without them

Explanation:

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.