Mitosis results in producing two cells which are similar to each other. What would be the consequence if each of the following irregularities occur during mitosis?
$(a)$ Nuclear membrane fails to disintegrate
$(b)$ Duplication of $DNA$ does not occur
$(c)$ Centromeres do not divide
$(d)$ Cytokinesis does not occur

(N/A) If the nuclear membrane fails to disintegrate,spindle fibers cannot interact with the chromosomes to pull them toward opposite poles. In some protozoans,this is a normal process called intranuclear mitosis,but in typical somatic cells,it prevents proper segregation.
$(b)$ If $DNA$ replication does not occur during the $S$-phase,the cell will lack the necessary genetic material to divide. Consequently,the cell cannot enter the $M$-phase,and the cycle arrests.
$(c)$ If centromeres do not divide,the sister chromatids will not separate. One daughter cell will receive both chromatids,while the other will receive none,leading to aneuploidy (such as trisomy or monosomy) in the resulting cells.
$(d)$ If cytokinesis does not occur after nuclear division,the cell will contain multiple nuclei within a single cytoplasm,resulting in a multinucleated condition known as a coenocyte or syncytium,as seen in organisms like $Rhizopus$ and $Vaucheria$.