You wanted to know whether the expression of a specific gene in different areas

Question

You wanted to know whether the expression of a specific gene in different areas of the brain could enhance memory. You are working with fruit flies and have devised a simple memory test that can be conducted with ease. Describe how you would achieve specific expression using the GAL 4 UAS system and why this would be a powerful approach. In addition describe how you would use in situ hybridization to confirm that you were expressing the gene where you thought you were. Finally describe how the second part would be done differently if you used GFP as a reporter gene instead on in situ hybridization.

Explanation / Answer

The term molecular genetics is now redundant because contemporary genetics is thoroughly molecular. Genetics is not made up of two sciences, one molecular and one non-molecular. Nevertheless, practicing biologists still use the term. When they do, they are typically referring to a set of laboratory techniques aimed at identifying and/or manipulating DNA segments involved in the synthesis of important biological molecules. Scientists often talk and write about the application of these techniques across a broad swath of biomedical sciences. For them, molecular genetics is an investigative approach that involves the application of laboratory methods and research strategies. This approach presupposes basic knowledge about the expression and regulation of genes at the molecular level. Philosophical interest in molecular genetics, however, has centered, not on investigative approaches or laboratory methods, but on theory. Early philosophical research concerned the basic theory about the make-up, expression, and regulation of genes. Most attention centered on the issue of theoretical reductionism. The motivating question concerned whether classical genetics, the science of T. H. Morgan and his collaborators, was being reduced to molecular genetics. With the rise of developmental genetics and developmental biology, philosophical attention has subsequently shifted towards critiquing a fundamental theory associated with contemporary genetics. The fundamental theory concerns not just the make-up, expression, and regulation of genes, but also the overall role of genes within the organism. According to the fundamental theory, genes and DNA direct all life processes by providing the information that specifies the development and functioning of organisms. The basic theory associated with classical genetics provided explanations of the transmission of traits from parents to offspring. Morgan and his collaborators drew upon a conceptual division between the genetic makeup of an organism, termed its genotype, and its observed manifestation called its phenotype (see the entry on the genotype/phenotype distinction). The relation between the two was treated as causal: genotype in conjunction with environment produces phenotype. The theory explained the transmission of phenotypic differences from parents to offspring by following the transmission of gene differences from generation to generation and attributing the presence of alternative traits to the presence of alternative forms of genes. I will illustrate the classical mode of explanatory reasoning with a simple historical example involving the fruit fly Drosophila melanogastor. It is worth emphasizing that the mode of reasoning illustrated by this historical example is still an important mode of reasoning in genetics today, including what is sometimes called molecular genetics. Genes of Drosophila come in pairs, located in corresponding positions on the four pairs of chromosomes contained within each cell of the fly. The eye-color mutant known as purple is associated with a gene located on chromosome II. Two copies of this gene, existing either in mutated or normal wild-type form, are located at the same locus (corresponding position) in the two second-chromosomes. Alternative forms of a gene occurring at a locus are called alleles. The transmission of genes from parent to offspring is carried out in a special process of cellular division called meiosis, which produces gamete cells containing one chromosome from each paired set. The half set of chromosomes from an egg and the half set from a sperm combine during fertilization, which gives each offspring a copy of one gene from each gene pair of its female parent and a copy of one gene from each gene pair of its male parent.

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