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Chapter 10: Chromosomes

Exercise 10.2 - Salivary Gland Preparation (Squash technigue)


Figure 10.2 Fruit fly larva



  1. Select a third instar larva, for which the cuticle has not yet hardened, from a wild-type culture of Drosophila. Place it into a drop of Ringer's saline solution on a slide.

  2. Place the slide on the stage of a dissecting microscope and view the larva with low power. Grasp the anterior of the larva with a fine point forceps and pin down the posterior portion with a probe. Gently pull the head off and discard the tail of the larva.

  3. Locate the salivary glands and their attached fat bodies. The glands are semitransparent and attached by ducts to the digestive system. The fat bodies are white and opaque. Tease away the fat bodies and discard.

  4. Place a drop of aceto-orcein on the slide next to the Ringer's and move the salivary glands into the stain. Blot away any excess Ringer's.

  5. Place a coverslip over the preparation and allow it to stand for 1-3 minutes (it will take a few trials to obtain properly stained chromosomes). Gently squash the gland preparation in the following manner:

  6. Examine the slide with the microscope and diagram the banding patterns that are observed.

  7. Compare your squash preparation to that of the prepared slides examined in Exercise 10.1.

  8. Repeat the squash technique using larva from a genetic variant known to be the result of a deletion and/or tandem duplication. Determine the location of the deleted or duplicated bands on the chromosomes.

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Cell Biology Laboratory Manual
Dr. William H. Heidcamp, Biology Department, Gustavus Adolphus College,
St. Peter, MN 56082 --