细胞分裂

Suspend an onion over a beaker of water and allow the roots to grow for several days before beginning the experiment. This growth period ensures roots are sufficiently developed and contain actively dividing cells in the meristematic zone, which is essential for observing different stages of the cell cycle in root tip cells.

Clean onion roots of any dirt or debris to remove contaminants that could interfere with microscopic observation and staining procedures. Removing surface material ensures clear visualization of cell structures and prevents artifacts that might obscure the identification of cells in different phases of division.

Dissolve 10 micrograms of nocodazole per 1 milliliter of dimethyl sulfoxide solution in a 1.5 mL tube, preparing one tube per student. This chemical solution arrests cells in mitosis, allowing students to observe and count cells in specific phases of the cell cycle during microscopic analysis.

Dimethyl sulfoxide serves as a solvent that effectively dissolves nocodazole, creating a stable working solution for the cell cycle experiment. This solvent allows the nocodazole to be properly distributed and absorbed by root tip cells, enabling consistent mitotic arrest across all experimental samples.

Set out all tools, materials, and reagents from the materials list onto each student's lab bench before the experiment begins. Proper organization ensures students have immediate access to everything needed for root tip preparation and observation, promoting efficient workflow and reducing experimental delays.

Root tips contain the meristematic zone, where cells actively divide and progress through all phases of the cell cycle. This region provides abundant cells in various stages of mitosis, making root tips ideal for observing and analyzing cell division patterns and identifying different phases of cellular division.

Nocodazole arrests cells in mitosis by disrupting microtubule formation, preventing progression through the cell cycle. This mitotic arrest accumulates cells in division phases, allowing students to observe and count cells in metaphase, anaphase, and telophase more easily during microscopic examination of root tip cells.