Human Genetics: Concepts and Applications (Lewis), 9th Edition

Chapter 8: Genetics of Behavior

Chapter Outline

CHAPTER OVERVIEW

1. Genes and environment contribute to human behavior.
2. Behavior-based disorders represent the extremes of normal behavior and are difficult to separate into genetic and environmental components.
3. Because symptoms of a number of behavioral disorders are similar, diagnosis may be difficult.
4. Candidate genes for behavior-based disorders are being sought among genes that control neurotransmission and signal transduction. Results may identify new drug targets.
5. Researchers are using genome-wide association studies to identify novel genes affecting behavior.
6. Assigning genetic causes to behavior is complicated by the complexity of traditional approaches to diagnosis.
7. Results from genetic studies are changing how behavioral conditions are diagnosed and categorized.
8. Researchers are combining traditional research methods, such as twin and adoptee studies, with molecular techniques to improve diagnosis and therapy.

1. Twin studies suggest that there is a considerable genetic component to eating disorders.
2. Genes that produce proteins involved with appetite control and neurotransmitters are candidates for the etiology of eating disorders.

1. Numerous genes appear to influence sleep, although the specific physiologic function of sleep is unknown.
2. Narcolepsy is caused by a single gene in dogs, but appears to be polygenic in humans.

1. A Utah family with a high prevalence of FASPS has provided evidence for a "biological clock" in humans.
2. A gene called "period" was located near the tip of the long arm of chromosome 2.
3. "Period" has counterparts in several species of animals.

1. Intelligence is an ill defined, but complex trait with genetic and environmental components.
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.

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.

1. Genes implicated in drug addiction are involved in biosynthesis of neurotransmitters, reuptake transporters, neurotransmitter receptors, and components of signal transduction pathways.
2. Genome-wide association and gene expression studies are revealing genes associated with addictive behavior and demonstrating possible patterns of gene expression during drug use.
3. Nicotine addiction has been used as a model for studying addictions in general.

1. Mood disorders represent the extremes of normal behavior and are difficult to separate into genetic and environmental components.
2. Because 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. Gene expression test are being developed to guide prescribing practices.
5. Although depression has been correlated with deficiencies in the serotonin transporter, assigning specific genes to bipolar disorder has been difficult.

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. Maternal infection during pregnancy is hypothesized to be a risk factor for schizophrenia.

1. Autism is not a single disorder but a spectrum of disorders
2. Discovering the genetic and environmental causes of autism has been difficult.
3. Familial studies have implicated genes encoding neuroligins and neurexins.