Question 1

What happens to chromosomes during prophase of mitosis?

Accepted Answer

During prophase, replicated chromosomes condense into visible threadlike structures with the aid of condensin proteins. Simultaneously, centrosomes migrate to opposite cell poles and begin forming the mitotic spindle apparatus from microtubules. The nucleolus disappears, signaling the impending breakdown of the nuclear envelope.

Question 2

How do kinetochores function during chromosome separation?

Accepted Answer

Kinetochores are protein structures on centromeres where spindle microtubules attach during prometaphase. During anaphase, kinetochore-attached microtubules shorten, pulling sister chromatids apart toward opposite cell poles. This separation is enabled by the breakdown of cohesion proteins holding the chromatid pairs together.

Question 3

What is the role of the metaphase plate in mitosis?

Accepted Answer

The metaphase plate is the cell's equatorial region where spindle microtubules align all condensed sister chromatid pairs in a fixed row during metaphase. This alignment ensures that each daughter cell receives an identical set of chromosomes. The metaphase plate marks the transition point before sister chromatids separate during anaphase.

Question 4

How does cytokinesis differ between animal and plant cells?

Accepted Answer

In animal cells, actin filaments form a contractile ring that pinches the cell into two, creating a cleavage furrow. In plant cells, Golgi vesicles carrying structural proteins form a cell plate at the former metaphase plate location, which fuses with plasma membranes to create a new cell wall dividing the cell.

Question 5

What occurs during telophase to prepare for cytokinesis?

Accepted Answer

During telophase, chromosomes decondense into chromatin at opposite cell poles, and spindle microtubules depolymerize into tubulin monomers for reuse in daughter cells. Nuclear envelopes reassemble around each chromosome set, restoring two distinct nuclei. These events prepare the cell for cytokinesis and the formation of two genetically identical daughter cells.

Question 6

What is the relationship between the spindle apparatus and chromosome movement?

Accepted Answer

The spindle apparatus is a web-like structure of microtubules that extends from centrosomes at opposite cell poles. Kinetochore microtubules attach to chromosomes and shorten during anaphase, pulling sister chromatids apart. Polar and astral microtubules push spindle poles apart, coordinating chromosome segregation and cell elongation throughout mitosis.

Question 7

How long does mitosis typically take in human cells?

Accepted Answer

Mitosis accounts for approximately one hour of the 24-hour cell cycle in most human cells. The complete cell cycle includes DNA replication during S phase and gap periods for cell preparation. This timing ensures coordinated, regulated progression through all mitotic stages from prophase through cytokinesis.

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