The Lab in Action
Transgenic worms expressing a myo-3::lacZ transgene
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Transgenic worms expressing a myo-3::lacZ transgene Here you see worms magnified about 20X that are expressing an added gene, the gene that encodes B-galactosidase. The expression of B-galactosidase is controlled by a promoter (on/off switch) from the myo-3 gene. We have exposed the worms to a substrate of the B-galactosidase enzyme; this substrate turns blue only in the presence of the enzyme. This way you can see exactly which cells of the animal have expressed the gene because the animal is transparent. This is a way of asking which cells normally use, or express, the myo-3 gene. In this case, the protein also contains a nuclear localization signal, so only the nucleus of each of the myo-3 expressing cells is blue. The large worm is oriented with its head (anterior) to the bottom, so you can see that only about 13 cells in the anterior end are expressing myo-3. You can also see that myo-3 expression is seen in both adults and larval (smaller) developmental stages. This is a very powerful technique used to figure out the function of particular genes. Students in my molecular biology course use sets of animals like this to learn about gene expression patterns while students in my lab create worms expressing fluorescently labeled proteins.
Microinjection of Mutant DNA to Produce Transgenic Worms
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Microinjection of Mutant DNA to Produce Transgenic Worms Undergraduates in my lab have learned to make mutant genes and do this microinjection technique. A single C. elegans worm is shown magnified about 40X, with anterior to the left. (Notice that you can see the internal organs – this is a transparent animal!) An injection needle (we make these easily) is shown pushing into the cuticle and the ovary of the animal. The ovary looks a bit like a dimpled golf ball – each dimple is the nucleus of a developing oocyte. The next step will be to poke the needle into the gonad and release some DNA into the ovary where it will be taken up by some of the oocytes to produce transgenic offspring.
