Final answer:
The minus end, or the 'B. minus end,' of a microtubule is embedded in the centrosome. It serves as an anchor point, while the plus end facilitates growth by addition of tubulin dimers. This polarity is crucial during mitosis or meiosis when microtubules form the mitotic spindle and disassemble at the minus ends to separate chromosomes.
Step-by-step explanation:
The end of a microtubule that is embedded in the centrosome is known as the minus end, or the 'B. minus end.' This is because microtubule polarity is such that the plus end is the site of growth, where α/β-tubulin dimers are added, and the minus end is the site typically anchored at organizing centers like the centrosome or centrioles.
During cell division, specifically mitosis or meiosis, microtubules reorganize to form the mitotic spindle. The spindle fibers are nucleated from centrosomes in animal cells, which are composed of two centrioles at right angles to each other, each with a '9 triplet' microtubule array. These centrosomes serve as microtubule-organizing centers, with the spindle's minus ends disassembling at the centrosomes to generate the force needed for chromosomal separation.