Genetic engineering has allowed biologists to study how genes function. For example, researchers in Montreal used genetic engineering to study brain development in mice. They wanted to determine what activates the gene Hoxd4 as the hindbrain develops in an embryo. This is important because abnormal hindbrain development may contribute to autism, a disorder that disrupts a child's ability to socialize and communicate.
The researchers combined the Hoxd4 gene and a region adjacent to the gene with a "reporter gene." The reporter gene encodes an enzyme that can make a blue-colored product. They inserted the recombinant DNA into mouse cells, grew embryos, and found that the region adjacent to the Hoxd4 gene could turn on the reporter gene and its blue product, as shown in Figure 13-10a. When they mutated the adjacent region, they discovered (by the lack of blue color) that it was expressed in the spinal cord, but not in the embryo's hindbrain, as shown in Figure 13-10b. They concluded that the DNA sequence adjacent to Hoxd4 helps control hindbrain development. Experiments such as these are unraveling the mysteries of gene function during development and may eventually provide therapies for disease.
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Autism is a developmental disorder that manifests itself in early childhood and affects the functioning of the brain, primarily in the areas of social interaction and communication. Children with autism look like other children but do not play or behave like other children. They must struggle daily to cope and connect with the world around them.