Question

the spindle fibers attach to chromosomes at the ______.
a chromatid
b centromere
c centrosome
d aster

Explanation:

To solve this, we analyze each option:

• Option A: A chromatid is one half of a replicated chromosome, not the attachment site for spindle fibers.
• Option B: The centromere is the region on a chromosome where spindle fibers attach during cell division (like mitosis/meiosis), which matches the question's context.
• Option C: A centrosome is an organelle that organizes microtubules (including spindle fibers) but is not the attachment site on the chromosome.
• Option D: An aster is a radial array of microtubules from the centrosome, not related to chromosome attachment.

Answer:

B. centromere