Materials 21 Solutions

1. Dissecting saline: 0.7% NaCl in water (see Note 1).

2. Lacto-aceto-orcein: You can probably borrow some from a co-worker when you first begin but eventually you are going to have to make your own. There are many recipes, the following is mine:

Put 2 g of Gurr's synthetic orcein into 100 mL of 1 part 45% acetic acid, 1 part concentrated lactic acid. Reflux for 1 h (boiling beads help). Cool; do not filter. Store at room temperature in a glass bottle with a frittered glass stopper. Good until used up. This is the "rough" stain; it should give excellent staining and handling characteristics as is although each batch of stain will differ slightly.

^Dedicated to Dan L. Lindsley in appreciation for his much good advice, especially about the old shirt.

From: Methods in Molecular Biology, vol. 247: Drosophila Cytogenetics Protocols Edited by: D. S. Henderson © Humana Press Inc., Totowa, NJ

Place 1 mL in an Eppendorf tube, centrifuge it for 10 min in a microfuge to pellet the suspended stain crystals, and try it (see Subheading 3.1.). As long as it is not shaken it does not need to be filtered or centrifuged again, but if chunks of crud appear on the preparations you have shaken it; recentrifuge. If it is not satisfactory, the modification in Note 2 is at least one place to start.

Note: I am now using Lefevre's (1) no-cook orcein (slightly modified from the original recipe), with excellent results. Take 2 g of Gurr's synthetic orcein; add 50 mL glacial acetic acid, 30 mL of lactic acid, and 20 mL of distilled water. Let it sit on your desk for a couple of days, shaking it whenever you think of it. Centrifuge as above before use.

3. Fixative: One part glacial acetic acid to three parts 95% ethanol (see Note 3).

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