Prof. Greg Francis 6/16/081Basics of geneticsIIE 366: DevelopmentalPsychologyGreg FrancisLecture 04 Some physical traits are explained by the properties of a singlegene E.g., sickle cell anemia Such traits tend to have little variability But this is not the way most traits operate Moreover, almost all behaviors are influenced by many differentgenes and environmental factors How do we study these more complex traits and behaviors? How do we connect them to their genetic basis?Simple genetics There is variation across people in theirenjoyment of novel situations Characterized as a tendency to take risksNovelty seekingGenetic basis of novelty seeking There is some evidence that novelty seekingbehavior is connected to a gene that influences aneural receptor protein that is sensitive to thedopa mine neurotransmitter DRD4 Dopamine is known to be related toreinforcement in a wide variety of situations Pleasure seeking Drug addictionGenetic methods• We’re going to complete an activity thatdemonstrates how these kinds of conclusionsare drawn• Privately answer the questions on the hand out.• Do not write on the hand out itself, but on aseparate piece of paper count up how manyquestions you answer “yes” Now, write the number of “yes” responses onone of these sheets of paper Fold your sheet lengthwise and give it to me We will make a histogram of how often studentssay “yes” to the survey questionsSurvey resultsProf. Greg Francis 6/16/082 Describe the distribution of scores What is the average? How do scores differ?Survey results Why are there differences across individuals? What factors would influence novelty seeking? Genetics CultureDifferences Is the survey an accurate way to measure novelty-seeking? What might be a better measure? Reliability? Validity?Survey We know that height is related to genetic factors Tall parents tend to have tall children But there can be tremendous variation in heights We also know that environmental factors areimportant Nutrition influences height Can variation in personality traits (like novelty-seeking) be explained in a similar way?Traits / behaviors Identical twins are genetically identical (monozygotic) If identical twins have a very similar trait, then it may bereasonable to look at the genetics as an explanation forthe similarity. But how to factor out environmental factors? Twins are usually raised by the same parents Have similar experiences (e.g., schools, friends) Look for adopted-apart twins who live with differentfamiliesTwin studiesHeightProf. Greg Francis 6/16/083 Fraternal twins are not genetically identical(dizygotic) We can compare similarities between identicaland fraternal twins What would you expect a height scattergram tolook like for adopted-apart fraternal twins? What are the sources of variation?Fraternal twinsIdenticaladopted-apart twinsIs thereevidence for agenetic effect?Novelty-seeking behaviorFraternaladopted-apart twinsHow does thedata compareto the identicaltwins?What do thesedifferencesmean?Novelty-seeking behavior Mathematical measurements of the relationshipbetween twins for novelty-seeking find: Identical twins r=0.6 Fraternal twins r=0.23 Measures how changes in one twin can berelated to changes in the other twinCorrelations Does this data suggest that there agenetic influence on novelty-seeking? What influence does the environmenthave? What would happen if the identical twinswere adopted by very different families?Genetic effects Is novelty-seeking behavior likely to be based ona single gene or multiple genes? Why?Genetic effectsProf. Greg Francis 6/16/084 What other behaviors are likely to be influenced byboth genes and environment? Happiness? Depression? Anxiety? Drug abuse? Intelligence?Other behaviorsNext time Genetics and development Heredity Interactions between genes