A) replication of the genetic material
B) splitting of the chromatids
C) splitting of the centromeres
D) condensation of the chromatin
Correct Answer: C
Solution :
Cell cycle is the sequence of events by which a cell duplicates its genetic material, synthesizes the other constituents of the cell and eventually divides into two daughter cells. It is divided into two basic phases interphase and M-phase or mitosis phase. Interphase losts more than 95% of duration of cell cycle. It is the time during which the cell is preparing for division by undergoing both cell growth and replication of genetic material. It is further divided into \[{{\text{G}}_{\text{1}}}\text{-}\]phase, S phase and \[{{\text{G}}_{2}}\]phase. \[{{\text{G}}_{1}}\] phase corresponds to interval between mitosis and initiation of DNA replication. Durings S phase DNA synthesis or replication takes place and the centriole duplicates in cytoplasm. In \[{{\text{G}}_{2}}\] phase proteins are synthesized in preperation for mitosis, while cell growth continues. M phase is the actual cell division phase where mitosis occurs. It is divided into four stages Prophase, metaphase, anaphase and telophase. Prophase is the stage where chromosomal or chromatin material condeuses to form mitotic chromosomes which are seen to be composed of two chromatids attached together by a centromere. Centrioles which duplicated in s phase, move towards opposite poles and initiate formation of spindle network. Metaphase is characterised by complete disintegration of nuclear envelope, chromosomes attach to spindle network by kinetochores of centromeres and move to spindle equator to get aligned along the metaphasic plate. Anaphase is characterised by splitting of the centromeres and separation of chromatids. Chromatids move to opposite poles from the equatorial plates. Telophase is characterized by clustering of the chromosomes at opposite poles, re assembly of nuclear envelope and reformation of the nucleolus, golgi complex and endoplasmic reticulum. After telophase, division of cytoplasm by a cleavage furrow which appeared at begining of telophase takes place. This phenomenon is termed as cytokinesis.
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