Biology

Standard IV, Objective 3

Title: Mutant Radishes

Description: Students will germinate radishes that that have been irradiated and determine what dosage of radiation will affect them.

Materials: 20 control (normal) radish seeds, irradiated radish seeds (available from most scientific supply catalogs), petri dish, paper towels, small beaker

Time Needed: Part 1: set up day 50 minutes, daily checks-10 minutes over two weeks. Part 2: same

Safety concerns: Make sure students are using a safe source of irradiation. Check their procedures before allowing them to proceed.

Procedures:

1. Procure the radish seeds by ordering them or if you have a source of radiation (access to X-ray machine in hospital or airport), radiate your own.

Collect the materials, copy student sheets.

2. Read the introduction and procedures on student sheets with students. The lab is written so that each group only tests two of the 4 types of irradiated seeds. This will save money but if you have lots of that, each group can do all four types of seeds.

3. Allow time for groups to set up the dishes and place in the designated place.

4. Students should observe the seeds for several days to make sure all the seeds that will germinate have time to.

5. Have students determine in their groups what type of radiation they will expose the next set of seeds to. You may need to help them determine what radiation is and where some sources are. It will be helpful to find an internet site or reading selection to help them.

6. Allow students to expose their seeds to the radiation they chose for the time periods they chose.

7. The newly irradiated seeds should be planted in dishes and labeled. They should be allowed to grow for several days until results seem clear.

8. Have students report by group to the class on their results and what they think they mean.

Student Sheet

Title: Mutant Radishes name______

Introduction: Scientists have known for some time that radiation is harmful to DNA and can cause mutation. Sometimes the mutation is positive and the organism is better able to survive. Most often, mutations are harmful. In this activity you will germinate radish seeds that have been radiated to different degrees. Radiation is measured in “rads”. The more rads, the more radiation the seeds have received. You will see the effect of radiation on radish seed germination and growth and see if more radiation produces more mutations. You will also choose a form of radiation to expose seeds to and design your own experiment.

Materials: control radish seeds, irradiated radish seeds, petri dishs, paper towels, small beaker

Procedure, Part 1

1. Label the lid of your petri dishes. One is control, the other two are the tests. On the test lid write the number of rads your seeds had. You are assigned ______rads and ______rads

2. Observe the radish seeds for the next 8 days. Record observations on data sheet. Trade dishes with other groups for the ones you don't have.

3. On the final day, pick a seedling that represents each dish and draw it.

Prediction: How will the radiation affect the germination and growth of radishes?

Data:

Dish / Date / Observations and final drawings
Control
50,000 rads
150,000
rads
500,000 rads
4,000,000
rads

Procedure, Part 2

1. With your group, research and decide what type of radiation you would like to expose some radish seeds to.

2. Decide the length of time they will be exposed.

3. You will have about a week to radiate the seeds. Some may need to be exposed the entire time, depending on the form of radiation you chose.

4. Have the seeds ready on the date your teacher asks.

Your procedures:

5.

6.

7.

8.

9.

10.

Your data:

Radish Analysis:

Part 1

1. What was the main difference between the control seedlings and the irradiated seeds?

2. How did increasing the amount of radiation affect the radishes?

3. Where does radiation come from in nature?

4. What controls seed development and growth?

5. Do you think these results would be useful in determining the effect of radiation on people? Why?

6. Why would an experiment that would provide information regarding the effects of radiation on people be difficult to do?

Part 2

7. How did the radiation your group chose affect radishes?

8. If you were going to do the experiment over, what would you do differently?

Conclusion: