Materials

Growing root tips of the broad bean,V. faba (2n=12)

Solutions of chromosome-damaging agents listed in the introduction to this Chapter

Reagents for Feulgen stain (Exercise 2.5)

Oven at 60° C

Microscope

Procedure

1.Place freshly germinated bean seedlings into petri plates containing serial diluted samples of suspected chromosome damaging agents.

2.Remove a seedling, rinse with distilled water and cut off root tips. Place the root tips into 1 N HCl, 60° C, for 10 minutes.

3.Rinse the root tip and place in Schiff's reagent in dark for 30 minutes.

4.Rinse the tip again, blot it gently and very gently rub the extreme tip of the root to remove the root cap.

5.Place the root tip into a drop of 45% acetic acid on a clean slide and macerate the tissue with a razor blade.

6.Place a coverslip over the macerated tissue and squash as in the procedure for the Drosophila polytene chromosomes (Chapter Ten).

7.Identify as many types of chromosome damage as found, referring to Figure 11.5. Draw and label representative views.

8.Use the caffeine treated cells to count the number of abberrations appearing per 100 anaphases examined and record the data in this manner (i.e. number of abnormalities per 100 anaphases examined).