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How can we manipulate genes in flies?
How can we manipulate genes in flies?
The genes on the DNA carry all information about everything an organism needs to do. Each cell in our body has the same genes, but genes can be switched off or on depending on function of cell. Therefore, a skin cell can do different things from a brain cell. If you want to know more, read here.
Each gene has a regulatory sequence: a piece of DNA that can switch the gene on or off. If it is switched on, the gene makes a protein – proteins are the molecules that do everything a cell has to do. To switch on or off genes, a special kind of protein is used: a transcription factor. It binds to the regulatory sequence of a gene and switches it on. The transcription factor, being a protein, is made by its own gene somewhere else on the DNA.
Yeast, the little organisms that can make cakes fluffy and produce alcohol, also have transcription factors and genes. One transcription factor is Gal4, and it binds to a regulatory sequence called UAS (Upstream Activation Sequence).
Scientists can take the gene for Gal4 from yeast and place it behind the regulatory sequence of a fly gene. This then can be integrated into the DNA of a fly. Scientists also can take the UAS sequence from yeast and place it together with any gene they are interested in. This can be any gene, from any plant, animal or human. This gene is called the effector gene.
Like this, the scientists created to kinds of fly: one, the driver fly, will produce the Gal4 protein under the control of the fly regulatory sequence. This means, the Gal4 will be made where-ever the original fly gene is made. For example, in the brain. But the fly has no UAS sequence anywhere in its genome, so the Gal4 is without function. The second fly, the effector fly, has the UAS sequence and the effector gene. But without Gal4 to bind the UAS, the effector gene will be inactive.
Only if these two flies are crossed to each other, their offspring will get one copy of the Gal4 gene, and the effector gene with the UAS. Thus, in the offspring, the Gal4 will bind to UAS, and the effector gene is switched on. The effector protein is made where-ever Gal4 is made.
So, scientists can insert and activate any gene, from any other organism, into any cell of the fly. This can be used to study the functions of the gene. Or the gene can be used to manipulate the cells it is active in. There are genes to make a cell shine green, or to kill a cell, or to remote-control a brain cell. The possibilities are endless!
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