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ANSWERS TO REVIEW QUESTIONS CHAPTER 8 1. Neurons transmit electrochemical messages. Neuroglial cells support neurons in several ways. 2. Behavioral traits are multifactorial because they reflect the complex interaction of genetic factors, responses to environmental stimuli, and learning. 3. Pathways involving neurotransmitters and signal transduction molecules affect behavior when absent or abnormal. 4. The behavior of altered sleep phase is clearly identifiable, occurs in many individuals across generations, and exhibits a clear mode of inheritance. 5. Drug addiction affects the nucleus accumbens, prefrontal cortex and ventral tegmental area of the limbic system. 6. We must understand how a gene variant affects behavior, and how other genes and the environment affect its expression. 7. Genetic heterogeneity; when a behavior is part of several disorders; behaviors that fall within the range of normal, although they are extreme; ability to imitate a behavior. 8. With age, the environment has had longer to affect gene expression than genetics. Socioeconomic and racial biases affected studies of the inherited component of intelligence. 9. Tolerance and dependence 10. Opiates bind receptors for endorphins and enkephalins, thereby relieving pain. 11. SSRls block reuptake of serotonin in synapses, correcting a deficit of the neurotransmitter that presumably causes the symptoms. 12. Bipolar disorder affects mood and symptoms include depression alternating with mania. Schizophrenia primarily affects thinking. 13. In humans, neurons have receptors for these drugs. 14. Maternal infection during pregnancy 15. A mutation in the cell surface receptor called hypocretin causes narcolepsy in dogs. 16. Autism may be subsumed by (part of) schizophrenia, separate from it, opposite it, or overlap it. 17. Drug addiction. Adoption and twin studies indicated a strong inherited component. GWAS point to variants in the dopamine D(2) receptor gene as well as candidate genes at 51 other sites in the genome. ANSWERS TO APPLIED QUESTIONS 1. a. The same neurotransmitter controls different behaviors. The differences arise from which neurons are involved. b. Dopamine 2. Identify what is abnormal in the Utah family, develop a drug to treat the condition, and then try the drug on people who are having difficulty sleeping. 3. The IQ test could be flawed, culturally biased, or measure intelligence in a way that does not compensate for differences in educational opportunities. 4. Mutations in genes for one subunit of the nicotinic receptor could affect functioning of a different subunit. 5. Evaluate the individual for evidence of tolerance and dependence. 6. A SNP profile indicating increased risk could be helpful if the person can take action to lower the risk of developing an addiction, but can be harmful if the person just gives up, thinking the fate cannot be avoided. SNP profiling might also be used to discriminate. 7. Depression and bipolar disorder each might actually be several conditions that have similar symptoms. 8. Environmental component about equals genetic susceptibility. 9. a. Environmental b. Chemical exposure, more children having their children evaluated for autistic behaviors. 10. NRXN1 encodes a cell surface protein involved in synaptic function; CHRNA3 and CHRNA5 are acetylcholine receptor genes, which also bind nicotine; CLCA1 encodes a calcium-activated chloride channel expressed in airway cells of smokers differently than non-smokers; CTNNA3 encodes a cell adhesion catenin protein; GABRA4 encodes the GABA receptor; KCNJ6 is a potassium channel. Variant ion channels and neurotransmitter receptors affect neurotransmission. ANSWERS TO WEB ACTIVITIES 1. Autism. Candidate genes encode neurexins and neuroligins. These proteins strengthen neural connections as a child learns and consolidates memories. 2. a. Results of validation studies using large samples and different population groups b. Provides an objective source of data c. Does not measure environmental effects 3. The participants were being treated for different conditions. Environmental factors differ between the two groups. Therefore genes and environmental factors are different between the two groups. 4. a. Small sample size b. Genome-wide association study of responders and non-responders c. Using the variant tryptophan hydroxylase-2 associated with calmness as a potential therapy for anxiety FORENSICS FOCUS 1. a. Opinion, but perhaps use genotyping if there is no other evidence, or as a way to explain a behavior. b. The high-activity allele for the enzyme MAO causes a deficiency of the three neurotransmitters, which can affect behavior. In the Dutch family that can’t make the enzyme, the levels of the neurotransmitters are too high. The levels of the three neurotransmitters must be within a certain range for behavior to be “normal.” c. Limitations are validity and generalizability CASE STUDIES AND RESEARCH RESULTS 1. The fact that DISC1 underlies schizophrenia and bipolar disorder supports the genetics approach because it indicates that the two disorders might not be as distinct as traditional psychiatry has considered them. Distinctions based on genetics could refine treatment choices. Perhaps a drug could be selected depending on genetics and the type of therapist selected based on symptoms. 2. a. Environmental b. Increased awareness and better screening c. identification of a SNP pattern that children with specific subtypes of bipolar disorder share. 3. Non-genetic cause. Genes may underlie the behavior which is modified by nongenetic influences on its expression. 4. Give the smoking cessation drug to a large number of people. Then determine whether CYP2A6 fast-metabolizers are over-represented among the people who respond. The participants should not know their genotypes. 5. The study cannot be evaluated without knowing the number of participants, and the incidence of the repeat in the gene in the general population. The study doesn’t show if the people who drank responded to the cues or just wanted the drinks.