(See related pages)
|
|
|
| 8.1 Genes Contribute to Most Behavioral Traits 1. Until recently studies on behavior were limited to empiric risk estimates and adoptee and twin studies. Now SNP (single nucleotide polymorphism) patterns can be correlated with disease symptoms. 2. Candidate genes for behavior control are being sought among genes that control neurotransmission and signal transduction. 3. Because of the complexity and plasticity of human behavior, caution must be exercised in assigning a genetic cause to a behavior. 8.2 Eating Disorders 1. Twin studies suggest that there is a considerable genetic component in eating disorders. 2. Genes that produce proteins involved in appetite control are candidates for the etiology of eating disorders. 8.3 Sleep 1. Numerous genes appear to influence sleep, although the necessity for sleep is unknown. 2. Narcolepsy is prevalent in some families, but has clearly been shown to be an autosomal recessive gene in dogs. 3. A Utah family has provided the first evidence for a "biological clock" in humans. A gene called "period" was located near the tip of the long arm of chromosome 2. 4. "Period" has counterparts in several species of animals. 8.4 Intelligence 1. Intelligence is an ill defined, but complex trait with substantial genetic and environmental effects. 2. IQ tests were first developed in the early 1900s. 3. IQ scores are a useful predictor of success in school, but caution must be exercised in labeling individuals or groups of individuals. 4. Genetic disorders that affect neurological function can affect intelligence in patients. 5. Single genes that affect intelligence are the subject of an intensive search. A few candidate genes have been identified. 8.5 Drug Addiction 1. Drug addiction is a compulsive behavior that exhibits tolerance and dependence. 2. Imaging techniques have identified regions of the brain involved in drug addiction. 3. Genes implicated in drug addiction are involved in biosynthesis of neurotransmitters, reuptake transporters, neurotransmitter receptors, and components of signal transduction pathways. 4. DNA microarray tests are revolutionizing the analysis of addictive behavior and demonstrating the pattern of gene expression during drug use. 8.6 Mood Disorders 1. Mood disorders represent the extremes of normal behavior and are difficult to separate into genetic and environmental components. 2. Because the symptoms of a number of mood disorders are similar, diagnosis may be difficult. 3. Depression and bipolar disorder may both involve a deficiency of serotonin. 4. Selective serotonin reuptake inhibitors (SSRIs) have become popular treatments replacing older tricyclic drugs. 5. Although depression has been correlated with deficiencies in the serotonin transporter, assigning specific genes to bipolar disorder has been difficult. 8.7 Schizophrenia 1. Schizophrenia may be difficult to diagnose, but generally affects thinking rather than mood. 2. High heritability and risk of recurrence suggest a genetic component to schizophrenia. 3. Concordance in identical twins also demonstrates that a significant environmental component exists in schizophrenia. 4. Familial studies have implicated numerous loci in schizophrenia. 5. Dopamine and glutamate levels are altered in schizophrenics. |