Mitotic Index Root Tip Squash

Summary

This video demonstrates how to observe mitosis by preparing a root tip squash, using onion or garlic roots. The process involves cutting root tips, adding hydrochloric acid and acetic orcin stain, and heating the mixture to allow the stain to penetrate the root tips. The root tips are then squashed on a microscope slide to make a thin layer, allowing for clear observation of various stages of mitosis. The viewer is guided through identifying the stages, including interphase, metaphase, anaphase, and telophase, while explaining why staining is crucial for increasing contrast and making chromosomes visible.

Takeaways

• 😀 Root tips are used for observing mitosis because they contain meristem tissue where cells are actively dividing.
• 😀 Onion or garlic roots are suitable for this process due to their visible root tip growth in water.
• 😀 The first step is to cut 5-10 mm of root tips and place them in a watch glass for further treatment.
• 😀 Hydrochloric acid is added to the root tips before staining to prepare them for the next steps.
• 😀 Acetic Orin stain is used to enhance the contrast of chromosomes in the root tips.
• 😀 The mixture is heated gently on a hot plate for 5 minutes to allow the stain to penetrate the root tips.
• 😀 The purpose of staining is to increase the contrast so that the chromosomes become visible under the microscope.
• 😀 After heating, the stained root tips are transferred to a clean microscope slide and covered with a cover slip.
• 😀 Pressure is applied using a folded paper towel to squash the root tip, making the sample thin enough for light transmission.
• 😀 Observing the slide under a microscope allows the identification of different mitosis stages, such as metaphase, anaphase, and telophase.

Q & A

Why are root tips used in the process of observing mitosis?

Root tips are used because they contain meristematic tissue, where cells are actively undergoing mitosis, making it an ideal location for observing the stages of cell division.

What is the first step in preparing a root tip for observation under the microscope?

The first step is to cut approximately 5 mm of root tips and place them in a watch glass.

Why is hydrochloric acid added before the acetic Orin stain?

Hydrochloric acid is added to soften the root tips, which helps the stain penetrate the cells more effectively.

What is the purpose of using acetic Orin stain in this procedure?

The acetic Orin stain increases contrast, making the chromosomes more visible under the microscope, which is crucial for identifying different stages of mitosis.

How should the root tips be heated during the preparation process?

The root tips should be heated gently on a hot plate for 5 minutes, ensuring that the liquid does not dry out, while allowing the stain to penetrate the root tips.

What happens if the heating step is not done properly?

If the heating is not done properly, the stain may not penetrate the root tips effectively, and the liquid may dry out, which would hinder the observation of mitosis.

What role does the paper towel play when preparing the root tip squash?

The paper towel is used to blot dry the slide while also applying pressure to form a thin squash, which is necessary for observing the cells under the microscope.

Why is it important to form a thin squash of the root tips?

A thin squash is important because it allows light to pass through the cells, making it easier to observe the stages of mitosis under an optical microscope.

What does it mean if the nucleolus is visible in the cells?

The presence of a visible nucleolus indicates that the cell is in interphase, as the nucleolus typically disappears during mitosis.

What are some of the stages of mitosis that can be observed in the root tip cells?

The stages of mitosis that can be observed include interphase, metaphase, anaphase, and telophase. Prophase can be harder to spot but is still identifiable under certain conditions.

What makes the observation of prophase challenging in this experiment?

Prophase can be difficult to observe because the chromosomes are only just becoming visible and the nuclear envelope is starting to disintegrate, making it harder to distinguish at this stage.

Why might this procedure be challenging to get right?

The procedure can be challenging because getting the root tips to squish evenly and thinly is difficult, and the timing of the staining and heating process needs to be precise for successful observation of mitosis.