Onion root tip cells are widely used in laboratories for studying cell division. Cells in the meristematic zone of onion plants divide rapidly, with large chromosomes making them easily visible under a microscope, making them ideal for studying mitosis (the process by which two identical cells form from a single original cell). Furthermore, these meristem cells are readily available year-round at reasonable costs and relatively straightforward to grow and handle; their spontaneous aberration frequency serves as an indicator of potential genetic damage to be assessed against.
Students conducting this experiment will observe the effect of various concentrations of cyanamide (CA) on mitotic index in onion root tip cells and analyze its impact on DNA content analysis using a Partec CCA flow cytometer for five biological replicates per sample. Results demonstrate that CA significantly decreases mitotic index while simultaneously decreasing DNA content – both effects being seen at five biological replicates per sample analyzed with CA. It does not, however, inhibit proliferation of meristematic cells or alter their arrangement within their respective root tip cells.
For this experiment, a small section of onion root meristem is cut off and placed on a microscope slide, before being submerged in a solution that softens it so it can be squashed flat on to it for microscopic observation. Following this step, an aceto-orcein stain is added which binds tightly with chromosomes so they are more visible under microscope observation.
Next, observe as root tip cells progress through each stage of mitosis – prophase, metaphase, anaphase and telophase – of mitosis. Each stage has its own distinctive structures which students will learn how to identify by viewing slides under a light microscope.
To summarize, this experiment aims to teach students the significance of cell cycle regulation on cancer incidence. Furthermore, students will become acquainted with cell walls – unique features present only in plant cells but essential for growth and development – which allow plants to thrive and prosper. Finally, students can practice using STEVE tools for measuring cell size and volume comparison as part of scientific method.