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Human Genetics. Concepts and Applications Seventh Edition. Powerpoint Lecture Outline. Ricki Lewis Prepared by Mary King Kananen Penn State Altoona. Chapter 8 The Genetics of Behavior. Behavior . Some behaviors may be transmitted from parent to child

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Human Genetics


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human genetics

Human Genetics

Concepts and Applications

Seventh Edition

Powerpoint Lecture Outline

Ricki Lewis

Prepared by

Mary King Kananen

Penn State Altoona

behavior
Behavior
  • Some behaviors may be transmitted from parent to child

Examples of behavioral traits include

    • Abilities, feelings, personality, and intelligence
  • Behavior is an interaction between the genes and the environment
  • Most are polygenic and multifactorial
  • It is difficult to determine the genetic contribution of a behavior and what is learned
behavioral genetics
Behavioral Genetics
  • Is the study of the nervous system (particularly the brain) variation and function
  • Uses empirical risk, twin studies, and adoption studies
  • Also, association studies with SNP and analysis of specific mutations that present in individuals with the behavior
neurons
Neurons
  • Sensory neurons
    • bring information to the brain
  • Interneurons
    • integrate information
  • Motor neurons
    • send information outward to muscles
  • Neurotransmitter
    • chemicals that communicate between neurons
attention deficit hyperactivity disorder adhd
Attention Deficit/Hyperactivity Disorder (ADHD)
  • Or attention deficit disorder (ADD)
  • Siblings of affected child show 3-5x greater risk than those without an affected sibling
  • Twins studies indicate ~80% heritability
  • Linkage analysis suggests changes in dopamine
  • Transporter and receptor proteins control dopamine levels
autism
Autism
  • Disorder of communication
  • Asperger syndrome is a related disorder
  • Studies have indicated 14 different chromosomes
  • Autism is probably several different disorders
eating disorders are a behavioral trait
Eating Disorders Are a Behavioral Trait

Anorexia nervosa

  • psychological perception of obesity and intentional starvation

Bulimia

  • psychological perception of obesity and intentional vomiting

Muscle dymorphia

  • results from steroid consumption to develop enlarged musculature
anorexia nervosa
Anorexia Nervosa
  • Women in U.S. have 5% lifetime risk
  • Risk of mortality is 15-21%
  • 2.5% risk of second eating disorder
  • 10% of cases are males
  • Heritability of 0.5 - 0.8
  • Concordance

9/16 MZ twins 1/14 DZ twins

genes affecting eating disorders
Genes Affecting Eating Disorders
  • Genes that encode proteins that control appetite, regulate some neurotransmitters (dopamine and serotonin) are candidates
  • SNP maps may identify regions that create a predisposition to eating disorders
sleeping disorders
Sleeping Disorders
  • Without sleep animals die
  • The function remains unclear
  • Genetic contributions are indicated by heritability among families and identification of genes in model systems
  • Twin studies indicate 4 of the 5 stages of sleep have a hereditary component
  • Environmental influence is great
narcolepsy with cataplexy
Narcolepsy with Cataplexy
  • Daytime sleepiness with tendency to rapidly fall
  • asleep (narcolepsy) and periods of muscle
  • weakness (cataplexy)
  • 1999, first gene identified with sleep in dogs
  • In Humans
  • Genetic contribution is indicated:
  • 0.02-0.06% general population in US and Europe
  • 1-2% risk with first degree relative
  • 25-31% concordance among MZ twins
familial advanced sleep phase syndrome
Familial Advanced SleepPhase Syndrome

Heterogeneic, but in this family, the condition is an autosomal dominant caused by a single base substitution

Figure 8.5

intelligence
Intelligence
  • Complex and variable trait subject to multiple genes and environmental influences and intense subjectivity
  • Refers to ability to reason, learn, remember, synthesize, deduce, create
  • 1904, IQ testdeveloped topredict academic success of developmentally handicapped children
  • Stanford University modified for white, middle-class Americans
  • IQ is normally distributed around a mean of 100.

below 50 severe mental retardation

50-70 mild mental retardation

85-115 average

above 115 above average

drug addiction
Drug Addiction
  • Compulsively seeking and taking a drug despite knowing its adverse effects

Characteristics

  • Tolerance

the need to take more of a drug to achieve the same effect

  • Dependence

the onset of withdrawal symptoms with cessation of drug

drug addiction1
Drug Addiction
  • Brain changes that contribute to addiction are in the limbic system
  • Drug addiction produces stable, not transient, changes in the brain
  • Heritability is 0.4-0.6
  • Twin and adoption studies support role of genes in drug addiction
proteins involved in drug adduction
Proteins Involved in Drug Adduction
  • Biosynthetic pathways of neurotransmitters in presynaptic neuron
  • Neurotransmitter reuptake transporters
  • Cell surface receptors
  • Signal transduction pathway in postsynaptic neuron
drug addiction2
Drug Addiction
  • A candidate gene codes for dopamine D(2) receptor
  • DNA microarray studies reveal many genes whose protein products affect neurotransmission, signal transduction, and myelin deposition on neurons
  • DNA expressions profiles may change with addiction to different drugs
mood disorders
Mood Disorders
  • Mood disorders represent the extremes of normal behavior.
  • Major depressive disorder

marked by unexplained lethargy and sadness and chronic depression

  • Bipolar affective disorder (manic-depression)

marked by depression interspersed with mania

mood disorders1
Mood Disorders
  • Serotonin, a neurotransmitter, can affect mood, emotion, appetite, and sleep
  • Many antidepressive drugs are serotonin reuptake inhibitors (SSRIs) including Prozac, Paxil, and Zoloft.
schizophrenia
Schizophrenia
  • A disorder marked by the loss of the ability
  • to organize thoughts and perceptions
  • leads to a withdrawal from reality
  • 1% of worldwide population is affected
  • Onset typically early adulthood
  • Progression of disorder:
  • Difficulty paying attention
  • Memory and learning skills affected
  • Psychosis (17-27 males, 20-37 females) delusions and hallucinations
schizophrenia is a multifactorial trait
Schizophrenia Is a Multifactorial Trait
  • Empiric risk estimates and heritability indicate a large genetic component
  • Concordance is high but a person with a schizophrenic MZ twin has a 52% of NOT developing the disease
  • Environmental associations important
  • Many candidate genes and genome regions
review
Review

Table 8.4