Onion Mitosis HSA San Antonio

This project has to deal with the six different phases of onion mitosis, and how to see what the differences are in the following six phases.

• 1. Interphase: DNA molecules of chromosomes(chromatin) replicating; chromosomes dispersed in nucleus as chromatin.

• 1. Prophase: Chromatin condenses into chromosomes.

• 1. Metaphase: Chromosomes line up on the equator of a cell; centromeres attach to spindlefibers; longitudinal separation of chromatids(now chromosomes) occurs; chromatids remain joined at centromere.

• 1. Anaphase: Centromeres divide; each set of chromosomes moves toward an opposite end of the cell.

• 1. Telophase: Spindle fibers disappear; chromosomes become diffuse; nuclear membrane and nucleolus reappear; cytokinesis(cytoplasmic division) occurs.

• 1. Daughter Cells: Mitosis and cytokinesis complete; two new cells in interphase result.

• • Materials:

  • Preserved onion root tips

  • 18% hydrochloric acid

  • Carnoy fluid

  • toluidine blue

  • microscope slides

  • coverslips

  • 30 disposable beakers

  • labels

  • paper towels or bibulous paper

  • droppers

  • razor blades or scalpels forceps

Obtain two small cups. Label one "HCI" and pour enough HCI into it to cover the bottom.

Label the other "Carnoy" and pour enough Carnoy fluid in it to cover the bottom.

Use forceps to transfer an onion root tip into the cup of HCI.

After 4 minutes, transfer the root into the Carnoy fluid. The root should remain in the Carnoy fluid for 4 minutes. After 4 minutes, place the root on the slide.

With a blazor or scalpel, cut off 1 to 2 mm of the root tip and discard all but this tip.

Cover the root tip with a few drops of toluidine blue for 2 minutes.

After 2 minutes, blot away the stain (without touching the root tip).

When the stain has been blotted away, cover the root tip with 1 or 2 drops of water.

Gently lower a coverslip over the root tip.

Cover the slide with a piece of paper towel or other absorbent paper and firmly press on the coverslip (without twisting it). The pressure will spread the cells into a single layer.

Observe your preparation under the low power of a microscope. If the cells are not sufficiently separated to permit viewing of each, squash the preparation again.

Try to observe sevaral cells in each stage. Now the important features characterisitcs of each stage.