Theory question 104
Cell Division(a) Describe the main stages of mitotic division. (b) State four ways in which mitosis is important to living organisms.
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(a) Interphase (preparation): chromosomes replicate.
Prophase: chromosomes shorten and thicken and become visible as two chromatids joined at a centromere; nuclear membrane and nucleolus disappear; spindle forms.
Metaphase: chromosomes line up on the equator of the spindle, attached by their centromeres.
Anaphase: centromeres split and the chromatids are pulled to opposite poles.
Telophase: chromosomes reach the poles; nuclear membranes re-form round each set; cytoplasm divides (cleavage furrow in animals, cell plate in plants), giving two identical daughter cells.
(b) Any four: growth of the organism; repair of damaged tissues and replacement of worn-out cells; asexual reproduction; keeps chromosome number constant; daughter cells are genetically identical, maintaining characteristics; regeneration of lost parts.
Name the stages in order: prophase, metaphase, anaphase, telophase.