Behavior Chapter 12. Central Points (1) Behavior is a reaction to environment Animals and humans...
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Transcript of Behavior Chapter 12. Central Points (1) Behavior is a reaction to environment Animals and humans...
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Behavior
Chapter 12
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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
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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
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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
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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?
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Animation: Communication among neurons
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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
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Synapse
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Drugs Mimic Neurotransmitters
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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
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Normal Brain and One with HD
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Chromosomal Abnormalities
Example: fragile X syndrome mutation on X chromosome
Causes autistic type behaviors as well as problems with aggression
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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
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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
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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
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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
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Concordance in Selected Traits
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Pedigree of Huntington Disease
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Animal Studies (1)
Mice reproduce quickly, behaviors are observable
May use recombinant DNA techniques
Insert a human gene
Mutate a mouse gene
Change gene’s pattern of expression
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Animal Studies (2)
Human gene for a protein associated with memory inserted into mice
Transgenic mice improved maze running and other tests
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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
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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
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Pedigree of Family with Violent Behavior
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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
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Knockout Mice
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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
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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
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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
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Adult and Teenage Brains
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Spotlight on Law: Mobley v. Georgia
Stephen Mobley on trial• Violent murder and armed robbery at Domino’s
• 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