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Chapter 3

chapter 3 psych notes

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Dan Dolderman

What Is the Genetic Basis of PsychologyGenetics in PsychologyThe processes involved in turning genes on and off Within every cell in the body is the genome genetic makeup for making the entire organismEach cell has a certain option what they do but this depends on the environment because the environment determines which options are taken what genes are turned on and off in a cell Within each cell are chromosomes structures made of genes Typical human has 23 pairs of chromosomes half of each pair coming from each parent Genes are components of DNA and the sequence of the genes produces a certain protein which carries out a specific task The environment determines what protein is produced and whenCells become specialized depending on which genes are expressed Gene expression determines bodys basic physical makeup and also specific developments throughout life and is involved in all psychological activity ex Learn fall in love etcHumans have just over 20000 genes Humans complexity is not due to the number of genes but rather to how these genes are expressed and regulatedWith the Human Genome Project researchers are now comparing different individuals genomes to how they vary specifically how variations in individuals genes determine whether someone is likely to develop specific disease or have some special ability Heredity Involves Passing Along Genes through ReproductionGregor Mendel was the first to discover clues to the mechanisms responsible for heredity transmission of characteristics from parents to offspring by means of genesHe developed selective breeding that controlled which plants bred with whichother plants He cross pollinated two different colored flowers purple and whiteto see what colour flower would be produced First generation either completely white or completely purple Second generation plants were purple flowers were produced 75 of the time because plants contained separate units genes existing in different variations colours Purple was dominant gene expressed in offspring whenever present and white was recessive only expressed when matched with a similar gene from the other parent Genotype Organisms genetic makeup determined at the moment of conception Phenotype Observable physical characteristics resulting from both genetic and environmental influences ex Skin colour may vary due to the sunPolygenic Effects characteristic is influenced by many genes and environment This variety shows the effects of multiple genes Ex variety in skin colours phenotype is not the end product of a single dominantrecessive gene pairing genotype those who receive a recessive gene from only one parent will have healthyphenotypes in spite of genotypes that include the diseaseGenes Affect BehaviourBehavioural Genetics Study of how genes and environment interact to influence psychological activityMonozygotic Identical Twins Result from the splitting of zygote share the same genes genotype and almost the same phenotypeDizyogotic Fraternal Twins Result from two separately fertilized eggs have different genotypes and phenotypesMonozygotic twins are more similar because of genetic influence Adoption Studies Compare the similarities between biological relatives and adoptive relatives Growing up in the same home turns out to have relatively little influence on many traits such as personality Minnesota Twin Project found that identical twins raised together or not were likely to be similar But twins and other relatives share similarities beyond coincidental attributes such as intelligence and personality tend to run in families because of strong genetic componentsTwins raised apart are in fact more similar due to environments Those raised togethertheir parents try and individualize them Heredity Transmission of characteristics from parents to offspring by means of genes Heritability Statistical estimate of the variation caused by differences in heredity in a trait within a populationSocial and Environmental Contexts Influence Genetic ExpressionA study done by Avshalom Caspi and his colleagues shows how nature and nurture together affect behaviour They did a longitudinal study proving that people with the enzyme MOA are more susceptible to the effects of maltreatment because low levels of MOA have been implicated in aggressive behaviours Genes predispose people to certain behaviours those behaviours elicit particular responses and those subsequent interactions then shape the phenotype Ex A wellmannered child signals more nurturing from parents than an irritable child Genetic Expression Can Be ModifiedResearchers can employ various gene manipulation techniques to enhance or reduce particular genes expression or even to insert genes from one animal species into embryos of another Such techniques have dramatically increased our understanding of how gene expression influences thought feeling and behaviour Ex scientists have created mice that are anxious hyperactive drink alcohol when stressed etc Changing one genes expression leads to the expression of a series of other genes influencing even complex behaviours
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