Final answer:
The M checkpoint delays anaphase in mitosis if chromosomes are not properly aligned, ensuring that sister chromatids are attached to spindle microtubules from opposite poles to prevent unequal segregation of genetic material.
Step-by-step explanation:
In mitosis, if a chromosome fails to become properly aligned at the metaphase plate, the M checkpoint, also known as the spindle checkpoint, will delay the onset of anaphase. The M checkpoint ensures that all sister chromatids are correctly attached to the spindle microtubules. If this connection is not secure, the cell will not proceed to anaphase because the separation of sister chromatids is an irreversible step. It is crucial for the kinetochores of each pair of sister chromatids to be anchored to spindle fibers from opposite poles of the cell.
If anaphase were to proceed without proper alignment and attachment of the chromosomes, it could lead to the unequal segregation of genetic material, resulting in daughter cells with abnormal numbers of chromosomes. Such errors during cell division can cause genetic disorders or contribute to the development of cancer due to chromosomal instability.