Question

what would happen if anaphase proceeded even though the sister chromatids were not properly attached to their respective microtubules and lined up at the metaphase plate?

Answer 1

If anaphase proceeded even though the sister chromatids were not properly attached to their respective microtubules and lined up at the metaphase plate, there will not be an equal number of chromosomes in each daughter cells.

The sister chromatids are attached to their respective microtubules and line up at the metaphase plate during metaphase for facilitating proper separation of sister chromatids during Anaphase. If the sister chromatids are not lined up at the centre correctly, there will not be an equal amount of chromosomes in the daughter cells. Before proceeding to anaphase, the cell will ensure the attachment of all the chromosomes' kinetochores to their respective microtubules. This is called the spindle checkpoint and helps to confirm that the sister chromatids will split evenly between the two daughter cells during Anaphase. If a chromosome is not properly lined up, the cell will halt division until the problem is solved as the separation of the sister chromatids during anaphase is an irreversible step.

If the spindle checkpoint were absent in cells, one or both of the new daughter cells would accidently possess extra chromosomes and/or would be lacking certain chromosomes.