Behavior Chapter 12 Central Points (1) Behavior is
Behavior Chapter 12 Central Points (1) Behavior is a reaction to environment Animals and humans have similar behaviors Brain chemicals important in human behavior
Single gene or groups of genes can affect behavior Central Points (2) Twin studies are an important part of behavioral genetics Courts are unclear on how to address the issue
of genetics and behavior Case A: Twins Found Strangely Alike University of Minnesota Twin Study Group, studying twins reared apart Two Jims: amazing number of physical and other similarities
Twin studies assist in the study of the genetics of behavior 12.1 Behavior A reaction to stimuli Human behavior similarities to animal behavior, response more variable, difficult to study
Behavioral genetics: study of the influence of genes on behavior Which more important: genetics or environment? Animation: Communication among neurons
12.2 Neurotransmitters Brain chemicals that can change our moods and actions Neurotransmission: Neurotransmitters released when certain neurons in the brain fire Impulse travels to synapse, neurotransmitter is released
Increases or decreases in the release of the neurotransmitter, may change behavior Synapse Drugs Mimic Neurotransmitters
12.3 Changes in Genes Changes Behavior Chromosomal abnormalities, single-gene defects, and multigenic conditions can alter behavior Example of single-gene defect: Huntington disease (HD) Codes for protein huntingtin, necessary for the survival of certain brain cells
Symptoms of HD: involuntary movements and progressive personality changes Normal Brain and One with HD Chromosomal Abnormalities Example: fragile X
syndrome mutation on X chromosome Causes autistic type behaviors as well as problems with aggression
Schizophrenia: A Multifactorial Condition Collection of mental disorders Many symptoms including hallucinations, delusions, disordered thinking, changed behavior Genes associated with schizophrenia found on X chromosome and other autosomes Also possible environmental component
12.4 Studying the Genetics of Behavior Search to find the genetic influences, also studied by psychologists and psychiatrists Medical geneticists study genetic basis for medical illnesses Differences between medical and behavioral
geneticists blurring Now treat depression as a physical illness Identical Twins (Monozygotic) Identical twins have identical genomes If a specific trait or behavior is same in both twins, most likely significant genetic component
If twins raised in separate environments and have different behavioral traits, traits have a significant environmental component Concordance in Monozygotic Twins If one identical twin is alcoholic, 55% chance other twin will be alcoholic regardless of environment
Concordance: how often a trait occurs in both members of a pair of twins Genetic trait, cystic fibrosis concordance = 1.0 Concordance helps establish whether or not trait has genetic basis Concordance in Selected Traits
Pedigree of Huntington Disease Animal Studies (1) Mice reproduce quickly, behaviors are observable May use recombinant DNA techniques Insert a human gene
Mutate a mouse gene Change genes pattern of expression Animal Studies (2) Human gene for a protein associated with memory inserted into mice Transgenic mice improved maze running and
other tests Case A Questions Why were these two men a perfect set of twins to study behavior? Do you think the evidence shows the behaviors listed in the case are 100% genetic?
Can you see any problems studying twins raised apart? See the textbook for further questions on this case 12.5 Single-Gene Defect and Aggressive Behavior Large family with aggressive and violent behavior
Only in men, many committed violent offenses Mapped to short arm of X chromosome Gene encodes monoamine oxidase type A (MAOA) that breaks down neurotransmitters Mutated form of gene, MAOA deficiency Pedigree of Family with Violent Behavior
Knock out Mice for Serotonin Receptors Failure to rapidly break down neurotransmitters such as serotonin Does not allow the normal transmission, disrupts normal functions in the nervous system Can cause abnormal behavior
Researchers deactivate (knock out) serotonin receptor gene in mouse Knockout mouse aggressive to unfamiliar mouse Knockout Mice 12.6 Legal and Ethical Issues
Not sure what causes aspects of behavior Courts finding it difficult to deal with topic Experts do not agree on findings, individual courts cannot decide how it will be used If certain genes or groups of genes cause someone to commit a crime, motive no longer relevant
XYY Syndrome Prisoners incarcerated for violent crimes showed higher percentage of men with XYY syndrome Studies done on relationship between criminality and XYY individuals Generally taller and perhaps more aggressive,
but this does not mean they are criminals Information incomplete Other Questions If criminal or antisocial behavior is genetically controlled, how can someone be rehabilitated? Roper v. Simmons: an amicus curiae brief
presented Area of brain controlling impulsive behavior underdeveloped in teens Therefore unable to realize actions Most judges and juries considered genetic predisposition to crime junk science
Adult and Teenage Brains Spotlight on Law: Mobley v. Georgia Stephen Mobley on trial Violent murder and armed robbery at Dominos History of rape, robbery, assault, and burglary
Aggressive behavior prevalent in his family Wanted to be tested for mutation of MAOA gene Court denied, genetic connection not at level of scientific acceptance to justify its admission
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