Question

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

Answer 1

Role of nuclear membrane disintegration

The disintegration of the nuclear membrane promotes the attachment of spindle fibres from the centriole to the chromosome and thus helps in their separation in later stages of cell cycle.

Consequences of absence of nuclear membrane disintegration

If the nuclear membrane does not disintegrate, spindle fibres will not attach to the centromere of chromosomes. This results in the failure of separation of chromosomes. This will further result in polyploidization.

DNA duplication

DNA duplication allows an equal amount of DNA distribution to both the daughter cells.

Failure of DNA duplication

Failure of DNA duplication will result in a halt of the cells from entering the mitotic phase. This is controlled by the checkpoints of the cell cycle.

Centromeres

Centromeres are located between the sister chromatids of a chromosome. These divide during anaphase of mitosis to split apart the sister chromatids.

Consequence of lack of division of centromere

If centromeres do not divide, the accurate separation of sister chromatids does not occur. This leads to failure of the accumulation of daughter chromosomes to the opposite poles. This results in chromosomal abnormalities in the daughter cells.

Cytokinesis

Cytokinesis is characterised by the division of the cytoplasm of the parent cell, finally completing the cell division and giving rise to two daughter cells.

Absence of cytokinesis

Failure of cytokinesis leads to multinucleated condition and coenocyte formation.