Neurogenetics

Neurogenetics studies the role of genetics in the development and function of the nervous system. It considers neural characteristics as phenotypes (i.e. manifestations, measurable or not, of the genetic make-up of an individual), and is mainly based on the observation that the nervous systems of individuals, even of those belonging to the same species, may not be identical. As the name implies, it draws aspects from both the studies of neuroscience and genetics, focusing in particular how the genetic code an organism carries affects its expressed traits. Mutations in this genetic sequence can have a wide range of effects on the quality of life of the individual. Neurological diseases, behavior and personality are all studied in the context of neurogenetics. The field of neurogenetics emerged in the mid to late 1900s with advances closely following advancements made in available technology. Currently, neurogenetics is the center of much research utilizing cutting edge techniques. Neurogenetics studies the role of genetics in the development and function of the nervous system. It considers neural characteristics as phenotypes (i.e. manifestations, measurable or not, of the genetic make-up of an individual), and is mainly based on the observation that the nervous systems of individuals, even of those belonging to the same species, may not be identical. As the name implies, it draws aspects from both the studies of neuroscience and genetics, focusing in particular how the genetic code an organism carries affects its expressed traits. Mutations in this genetic sequence can have a wide range of effects on the quality of life of the individual. Neurological diseases, behavior and personality are all studied in the context of neurogenetics. The field of neurogenetics emerged in the mid to late 1900s with advances closely following advancements made in available technology. Currently, neurogenetics is the center of much research utilizing cutting edge techniques. The field of neurogenetics emerged from advances made in molecular biology, genetics and a desire to understand the link between genes, behavior, the brain, and neurological disorders and diseases. The field started to expand in the 1960s through the research of Seymour Benzer, considered by some to be the father of neurogenetics. His pioneering work with Drosophila helped to elucidate the link between circadian rhythms and genes, which led to further investigations into other behavior traits. He also started conducting research in neurodegeneration in fruit flies in an attempt to discover ways to suppress neurological diseases in humans. Many of the techniques he used and conclusions he drew would drive the field forward. Early analysis relied on statistical interpretation through processes such as LOD (logarithm of odds) scores of pedigrees and other observational methods such as affected sib-pairs, which looks at phenotype and IBD (identity by descent) configuration. Many of the disorders studied early on including Alzheimer's, Huntington's and amyotrophic lateral sclerosis (ALS) are still at the center of much research to this day. By the late 1980s new advances in genetics such as recombinant DNA technology and reverse genetics allowed for the broader use of DNA polymorphisms to test for linkage between DNA and gene defects. This process is referred to sometimes as linkage analysis. By the 1990s ever advancing technology had made genetic analysis more feasible and available. This decade saw a marked increase in identifying the specific role genes played in relation to neurological disorders. Advancements were made in but not limited to: Fragile X syndrome, Alzheimer's, Parkinson's, epilepsy and ALS. While the genetic basis of simple diseases and disorders has been accurately pinpointed, the genetics behind more complex, neurological disorders is still a source of ongoing research. New developments such as the genome wide association studies (GWAS) have brought vast new resources within grasp. With this new information genetic variability within the human population and possibly linked diseases can be more readily discerned. Neurodegenerative diseases are a more common subset of neurological disorders, with examples being Alzheimer's disease and Parkinson's disease. Currently no viable treatments exist that actually reverse the progression of neurodegenerative diseases; however, neurogenetics is emerging as one field that might yield a causative connection. The discovery of linkages could then lead to therapeutic drugs, which could reverse brain degeneration. One of the most noticeable results of further research into neurogenetics is a greater knowledge of gene loci that show linkage to neurological diseases. The table below represents a sampling of specific gene locations identified to play a role in selected neurological diseases based on prevalence in the United States. Logarithm of odds (LOD) is a statistical technique used to estimate the probability of gene linkage between traits. LOD is often used in conjunction with pedigrees, maps of a family's genetic make-up, in order to yield more accurate estimations. A key benefit of this technique is its ability to give reliable results in both large and small sample sizes, which is a marked advantage in laboratory research. Quantitative trait loci (QTL) mapping is another statistical method used to determine the chromosomal positions of a set of genes responsible for a given trait. By identifying specific genetic markers for the genes of interest in a recombinant inbred strain, the amount of interaction between these genes and their relation to the observed phenotype can be determined through complex statistical analysis. In a neurogenetics laboratory, the phenotype of a model organisms is observed by assessing the morphology of their brain through thin slices. QTL mapping can also be carried out in humans, though brain morphologies are examined using nuclear magnetic resonance imaging (MRI) rather than brain slices. Human beings pose a greater challenge for QTL analysis because the genetic population cannot be as carefully controlled as that of an inbred recombinant population, which can result in sources of statistical error. Recombinant DNA is an important method of research in many fields, including neurogenetics. It is used to make alterations to an organism's genome, usually causing it to over- or under-express a certain gene of interest, or express a mutated form of it. The results of these experiments can provide information on that gene's role in the organism's body, and it importance in survival and fitness. The hosts are then screened with the aid of a toxic drug that the selectable marker is resistant to. The use of recombinant DNA is an example of a reverse genetics, where researchers create a mutant genotype and analyze the resulting phenotype. In forward genetics, an organism with a particular phenotype is identified first, and its genotype is then analyzed.