Exercise XXIV 



reagent. This is a mixture of alpha-/;ophthol 

 and ^/methyl-para-phenylenediamine (hence 

 "NADI"), which is oxidized to the blue pig- 

 ment, indophenol blue, by cytochrome oxidase 

 in the presence of oxygen. 



Remove an embryo from the yolk and rinse 

 it in warm saline solution. Draw off the saline, 

 and replace it immediately with warm NADI 

 reagent. Record the time. Now record the 

 time for the first trace of blue color to appear, 

 and continue to record its location and extent 

 at three-minute intervals. Compare the results 

 of your experiment with those of your partner 

 on an older or younger embryo. 



DEVELOPMENT OF THE CHICKS 125 



GENETICS EXPERIMENT 

 (continued: third week) 



At some time during this period, go the next 

 step in your Drosophila experiment. Last week, 

 flies of the Fi generation were mated. Today, 

 these parent flies should be removed from the 

 vials and disposed of in the morgues. Then 

 replace the vials in the boxes for further incuba- 

 tion. Next week this experiment will be com- 

 pleted. The F2 generation of adults will have 

 emerged, and the results of the experiment can 

 be analyzed. 



EQUIPMENT 



equipment for handling Drosophila as in Exercise 



XXII 



fertile eggs incubated for 3 and 5 days (I per student) 



prepared slides of chick development 



dissecting scope 



petri dish 



ringer solution, kept at 37°C (0.9% NaCl may be 

 substituted for ringer solution if there is no desire 

 to keep the embryo alive for an extensive period) 



NADI reagent 



Preparation of NADI reagent. This should be pre- 

 pared just prior to use. Combine equal parts of 

 0.01-M alpha-naphthol, 0.01-M dimethyl-/7-phenyI- 

 enediamine (PPD), and phosphate buffer, pH 5.8. 

 The alpha-naphthol is made by dissolving 1.44 gm 

 in 1 liter of physiological saline (0.9% NaCl solu- 

 tion). Heat to dissolve. The PPD solution contains 

 1.36 gm in 1 liter of physiological saline. The phos- 

 phate buffer is a mixture of Na2HP04 (9.5 gm/1 dis- 

 tilled water), and KH2PO4 (9.07 gm/l distilled 

 water), mixed in the proportions 7.8 mm Na2HP04 

 solution; 92.2 mm KH2PO4 solution. 



