Exercise 10.2 - Salivary Gland Preparation (Squash technigue)
Figure 10.2 Fruit fly larva
- Fruit fly larva (wild type and tandem duplication mutants)
- Ringers insect saline
- Fine forceps and probe
- Dissecting and regular microscopes
- Slides, coverslips
- Small dish of melted paraffin and paintbrush 2
- 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.
- 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
- 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.
- 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.
- 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
- Place the slide between several layers of paper toweling.
- Place your thumb on the top of the towel immediately over the
coverslip and gently roll your thumb while exerting a small
amount of pressure (as though you were making a finger print). Do
not move your thumb back and forth. One gentle roll is
- Remove the slide from the towels, and seal the edges of the
coverslip by using a paint brush dipped in melted paraffin.
- Examine the slide with the microscope and diagram the
banding patterns that are observed.
- Compare your squash preparation to that of the prepared
slides examined in Exercise 10.1.
- 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 -- firstname.lastname@example.org