Day 7: Jumpin' Genes!

Chromosomes Line up Along the Metaphase Plate

While DNA is replicating in the nucleus, work is going on in the cytoplasm in preparation for cell division. The cytoplasm contains small filaments and microtubules which, when called upon, link together like building blocks to form structures within the cells. When a particular structure is no longer needed, it is disassembled. These structures are components of the cell's cytoskeleton. When a cell is preparing to undergo mitosis, two special structures called centrioles take their places on opposite sides of the nucleus. The centrioles act like construction supervisors. Microtubules begin to assemble near the centrioles and radiate toward the nucleus in search of chromosomes. The resulting structure is called a mitotic spindle.

As construction of the mitotic spindle gets underway, the nuclear membrane dissolves and the long chromosome strands begin to coil and fold until the chromosome is a condensed package. A spindle fiber from each centriole will attach to the kinetochore on either side of the chromosome's centromere and the spindle will be complete. Together, the spindle fibers from either centriole guide the chromosome to the center of the mitotic spindle. This stage of mitosis is called metaphase and the arrangement of chromosomes lined up in the center of the mitotic spindle is referred to as the metaphase plate.

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