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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. 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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  1. Human Genetics Concepts and Applications Seventh Edition Powerpoint Lecture Outline Ricki Lewis Prepared by Mary King Kananen Penn State Altoona

  2. Chapter 8The Genetics of Behavior

  3. 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

  4. 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

  5. Table 8.1

  6. Neurons • Sensory neurons • bring information to the brain • Interneurons • integrate information • Motor neurons • send information outward to muscles • Neurotransmitter • chemicals that communicate between neurons

  7. Genes Control the Synthesis, Levels, and Distribution of Neurotransmitters Figure 8.2

  8. 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

  9. Autism • Disorder of communication • Asperger syndrome is a related disorder • Studies have indicated 14 different chromosomes • Autism is probably several different disorders

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. Figure 8.4

  16. Familial Advanced SleepPhase Syndrome Heterogeneic, but in this family, the condition is an autosomal dominant caused by a single base substitution Figure 8.5

  17. 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

  18. Intelligence Quotient (IQ) Figure 8.6

  19. Heritability of Intelligence Changes Over Time Table 8.2

  20. 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

  21. 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

  22. Figure 8.7

  23. Proteins Involved in Drug Adduction • Biosynthetic pathways of neurotransmitters in presynaptic neuron • Neurotransmitter reuptake transporters • Cell surface receptors • Signal transduction pathway in postsynaptic neuron

  24. 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

  25. 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

  26. 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.

  27. Figure 8.8

  28. 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

  29. 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

  30. Environmental Risk Factorsfor Schizophrenia Table 8.3

  31. Review Table 8.4

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