PSYC 4220 1st Edition Lecture 5 Outline of Last Lecture I Contextual Effects of Parenting Styles II Genetic Code III Meiosis IV Family Resemblance V Mitosis VI Determination of Sex Outline of Current Lecture I II Translation of Genetic Code Single Gene Pair Inheritance A Homozygous B Heterozygous III Sex Linked Inheritance IV Behavioral Genetics V Studying Hereditary Influences A Family Studies 1 Twin designs 2 Adoption designs Current Lecture Translation of Genetic Code Genotype genetic makeup a person inherits Phenotype characteristic or traits that are actually displayed Multifactorial transmission determination of traits by combo of genetics and environment genotype provides range within phenotype may be expressed Single Gene Pair Inheritance Some human characteristics influenced by only one pair of genes Dominant genes expressed when present mask effects of recessive genes Recessive genes not expressed when paired with a dominant gene but can still be passed to offspring 3 possible combinations of gene pairs 2 dominant genes 2 recessive genes 1 dominant and one recessive gene Homozygous both genes are same two recessive genes develop recessive trait 2 dominant genes develop dominant trait Heterozygous genes are diff 1 dominant gene one recessive dominant gene expressed but recessive gene can still be passed on Example Tongue Curling T dominant tongue curling gene T recessive gene not being able to curl tongue Father cannot curl tongue tt Mother can curl tongue Tt What is the chance offspring will be able to curl tongue Possible combos Tt Tt tt tt 50 chance will be able to curl tongue Sex Linked Inheritance x linked genes characteristics influence by single genes located on 23 rd sex chromosomes Because X chromosomes contain more genes than Y recessive genes carried on X chromosome in males are displayed no corresponding dominant gene on Y chromosome to mask them So males more likely to suffer from sex linked genetic abnormalities Genetic Complexity Single gene pair inheritance is complex Polygenic traits characteristics influence by multiple pairs of genes most things in psychology are like this i e susceptibility to depression many characteristics influenced by more than single pair Behavioral Genetics interested in hoe much genes and environment contribute to difference in behavioral traits behavioral geneticists estimate impact of 3 factors genes level of heritability shared environmental influences common home experiences shared by people who live together non shared environmental influences unique experiences not shared by people who live together Studying Hereditary Influences Selective Breeding studying genetic influences by determining whether traits can be bred in animals through selective mating oldest way to study hereditary influences Oldest way to study hereditary influences ex maze learning activity level emotion sex drive of mice Can t be done with humans for ethical reasons Family studies compare members within a family to see how similar they are on certain traits if trait is heritable expect that the greater the kinship between 2 family members the more similar they would be on that train kinship the extent to which 2 individuals have genes in common Types of Family Studies Twin designs compare identical twins share 100 of genes similar environment to fraternal twins share 50 of genes similar environment if trait is heritable identical twins more similar than fraternal twins because of greater kinship Concordance Rate of cases in which trait is present for one member of twin pair if it s present for the other Used when you wither have trait or don t Concordance rate higher for identical twins suggests genetic component to that trait Example homosexuality concordance rate 52 for identical twins 22 for fraternal twins Correlation coefficients used to assess relationship between 2 traits Higher correlation closer resemblance between 2 people on that trait Used when trait is continuous Example Intelligence 85 for identical twins raised together 7 for identical twins raised apart 6 for same sex fraternal twins raised together 35 for unrelated kids raised together Adoption design adoptees are compared with biological relatives and adoptive relatives adopted child shares no environmental experiences with biological family so similarities to biological family likely due to heredity adopted child shares no genetic material with adoptive family so similarities to adopted family due to shared environmental influences Common misconceptions about heritability estimates heritability estimates can tell you whether or not you inherited a given trait wrong These estimates are looking at the amount of difference between people on a trait that can be explained by the genes they inherited These estimates are only looking at populations of people not individuals Very heritable traits cannot be modified by environmental influences wrong Just because something is easily explained by genetic variation does not meant hat the environment can t modify that trait