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PSY 1102 Text Book Material.docx

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PSY 1102Textbook Notes Chapter 4Nature Nurture and Human Diversity Behavior Genetics Predicting Individual Differences oBehavior genetics is the study of the relative power and limits of genetic and environmental influences on behavioroThey study human differences and weigh the effects and interplay of heredity and the environment which is every nongenetic influence from prenatal nutrition to the people and things around usoGenes Our Codes for LifeEach somatic body cell contains the genetic material that codes for the entire bodyThe genetic material is found in the form of chromosomes which are threadlike structures made of DNA molecules that contain the genesEach person has 46 chromosomes or 23 pairs of chromosomes each divided into 1 from dad and 1 from momDNA deoxyribonucleic acid is a complex molecule containing the genetic information that makes up the chromosomesGenes are the biochemical units of heredity that make up the chromosomesa segment of DNA capable of synthesizing a proteinThey are small segments of giant DNA molecules We have 30000 or so genes which can be either active expressed or inactiveEnvironmental events turn on genes and they provide the code for creating protein molecules the building blocks of developmentAltogether our genes make up a genome the complete instructions for making an organism consisting of all the genetic material in that organisms chromosomes makes organisms unique We share 96 of our genome with chimpanzees and 994 of functionally important DNA sitesChimpanzees and bonobos share 99 of their genomes yet show distinct aggressive and passive behaviors respectively Most traits are influenced by genes interacting with the environment and these traits help explain both universal human nature and human diversityoTwin and Adoption Studies Identical Versus Fraternal Twins Identical twins are twins that develop from a single fertilized egg that splits in two creating two genetically identical organisms oHave the same genes however they dont always have the same number of copies of those genes one twin may be at a higher risk for some illnessesoMost identical twins share a placenta however 1 in 3 sets have two distinct placentas one of which may be more nourishingFraternal twins are twins that develop from separate fertilized eggsThey are genetically no closer than brothers and sisters but they share a fetal environment A person whose identical twin has Alzheimers disease has a 60 chance of getting the disease versus 30 for fraternal twinsIn extraversion outgoingness and neuroticism emotional instability identical twins are more similar that fraternal twins If you have a divorced identical twin your odds of divorcing are increased 55 times versus 16 times for fraternalSeparated Twins38 year separated twins Jim Lewis and Jim Springer were given tests measuring their personality intelligence heart rate and brain waves and were found to be virtually as alike as the same person taking the test twice Other twins reared apart have demonstrated amazing similar habits desires likes dislikes physical attributes abilities attitudes interests fears and overall personalityCompared to identical twins reared together those reared apart had somewhat different personalitiesCritics argue that you could find similarities between any two random people of same age sex and ethnicity that grew up in similar economic and cultural settingsBouchard states that separated fraternal twins do not exhibit striking similarities and notes that virtual twins sameage biologically unrelated siblings are also much dissimilar Biological Versus Adoptive Studies Adoption studies created two groups genetic relatives biological parents and siblings and environmental relatives adoptive parents and siblingsPeople who grow up together whether biologically related or not do not much resemble one another in personality In extraversion and agreeableness adoptees are more similar to their biological parents relative to their adoptive parents Macaque monkeys raised by foster mothers exhibit social behaviors that resemble their biological rather than foster mothersWhy does shared family environment have so little effect on childrens personalitiesDo sibling relationships amplify differencesIs it that siblings have very different combinations of genes despite sharing 50 of genesAlthough adoptive parents have little effect on a childs personality they do have an influence on their attitudes values manners faith and politics especially religionAdoptive homes are heavily screened eliminating child neglect and abuse and even parental divorce because of this most adopted children thrive especially infantsoTemperament and Heredity Temperament a persons characteristic emotional reactivity and intensity can be very telling about an individuals personality even as an infantDifficult babies are more irritable intense and unpredictable
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