AP BIOLOGY

Detailed explanation-1: -The structure involved in the formation of spindle fibres are centrioles. They exist in a pair close to the nucleus and are present only in the animal cell.

Detailed explanation-2: -In animal cells centrioles organise the pericentriolar material to produce microtubules including mitotic spindle fibres.

Detailed explanation-3: -Spindle fibers are the microtubules, centrosomes, and related structures that form during cell division, specifically in eukaryotic cells (those with a nucleus and membrane bound organelles).

Detailed explanation-4: -Answer and Explanation: Centrioles originated spindle fibers form a structure called mitotic spindle which designed to pull the sister chromosomes to the opposite poles of the dividing cell.