Publication No. 10421
Student Laboratory Kit
Materials Included In Kit
Acetic acid solution, CH3COOH, 1 M, 100 mL
Hydrochloric acid solution, HCl, 1 M, 100 mL
Schiff’s reagent dye, 100 mL
Sodium bisulfite solution, NaHSO3, 1 M, 100 mL
Microscope slides, 72
Pipets, Beral-type, 45
Additional Materials Required
Onion root tip
Actively growing onion root tips are required for this activity. Allow 2–4 days for new roots to grow. You may grow the roots ahead of time or you may have students grow them as a group and complete the activity days later.
As shown in the figure, push several toothpicks into the bulb to support the bulb on the rim of the cup. Add water to the cup during the root growing time as needed to keep the root area under water. The roots should be about 2 cm in length when they are ready to harvest. Have students remove entire lengths of root when cutting the roots from the onion. Do not have them cut just partial roots. This will prevent later students from removing a root that doesn’t have a root tip! After removing the entire root only the 1-cm tip should be cut off and used in the exercise. Several onions should provide enough root tips for an entire class.
Hydrochloric acid and acetic acid are toxic by ingestion and inhalation and severely corrosive to skin and eyes. Sodium bisulfite is slightly toxic and is a severe irritant to skin and tissue. Schiff’s Reagent Dye is a body tissue irritant. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Please review current Safety Data Sheets for additional safety, handling and disposal information.
Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. Chemicals used in this activity can be disposed of according to Flinn Suggested Disposal Methods as follows: hydrochloric acid, #24b; acetic acid, #24a; sodium bisulfite, #26b; and Schiff’s Reagent Dye, #26b. The small amounts rinsed off during the slide preparation can follow #26b.
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering PracticesPlanning and carrying out investigations
Disciplinary Core IdeasMS-LS1.A: Structure and Function
HS-LS1.A: Structure and Function
HS-LS1.B: Growth and Development of Organisms
Crosscutting ConceptsStructure and function
MS-LS1-4. Use argument based on empirical evidence and scientific reasoning to support an explanation for how characteristic animal behaviors and specialized plant structures affect the probability of successful reproduction of animals and plants respectively
Answers to Questions
Student answers will vary.
The DNA is located in the nucleus.
The nucleus is typically stained darker than other organelles.
The DNA is most visible during the S phase.
DNA is considered the molecule of life because it stores information in biological molecules of living organisms. It carries the information/instructions needed to guide the development of an entire organism.
DNA (deoxyribonucleic acid) has come to symbolize modern molecular biology. It is significant for understanding molecular genetics and the critical workings of all living things. A first step in DNA study involves the isolation, staining and examination of DNA with a microscope.
Cells are very small yet very complex. It is difficult to observe many cell organelles by simply viewing them with a microscope. Most organelles do not interfere with the passage of light through the cell. Therefore, most cells are nearly transparent when viewed through a microscope. For more than 300 years, biologists have worked to develop a variety of techniques and aids for enhancing the visibility of cell structures. One technique that helps make cell structures more visible is to apply stains.
Acetic acid solution, CH3COOH, 1 M, 2–3 drops
Hydrochloric acid solution, HCl, 1 M, 3–4 drops
Schiff’s reagent dye, 3–5 drops
Sodium bisulfite solution, NaHSO3, 1 M, 10–15 drops
Water, 30–40 drops
Microscope slides, 2
Onion root tip
Pipets, Beral-type, 3
Scalpel or razor blade
Hydrochloric acid and acetic acid are toxic by ingestion or inhalation and severely corrosive to skin and eyes. Sodium bisulfite is slightly toxic and is a severe irritant to skin and tissue. Schiff’s Reagent is a body tissue irritant. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory.
Student Worksheet PDF