Exam 2 Required Reading Outline Biosocial Criminology Beaver Chapter 2 Pg 50 70 Molecular Genetics Each polynucleotide consists of a sugar phosphate backbone and situated along each of the backbones is a sequence of nucleotides bases The protein is what is ultimately responsible for bringing about phenotypes Human Genetic Variation Differences in DNA sequences i e genotypic variance can result in differences in phenotypes i e phenotypic variance including differences in antisocial phenotypes o Another way of saying this is that genotypic variance has the potential to explain phenotypic variance Genes are inherited on threadlike structures called chromosomes Each gene is found on a specific location on a specific chromosome o The location where a gene is found is called a genetic locus o Ex A gene involved in the transmission of dopamine is found on chromosome 11 Short tandem repeats STRs Microsatellites o In summary microsatellites surface because of differences in the number of times that a short section of base pairs is repeated Variable number of tandem repeats VNTRs Minisatellites o Keep in mind that the key difference between microsatellites and Minisatellites is the number of base pairs that is included in the repeat sequence How Genotypic Variance Can Produce Phenotypic Variance Monogenic effect OGOD One Gene One Disorder o Single gene single phenotype o Ex sickle cell anemia and Huntington s disease o Monogenic effects can be due to recessive or dominant patterns of inheritance Polygenic effect o Same information as notes Pleiotropic effect o Ex the allele that causes the disorder phenyliketonuria PKU also causes hair to lighten o There is some research indicating that an allele of the dopamine transporter gene DAT1 is associated with increase in criminal involvement as well as increases in number of sex partners o It is likely that part of the covariation between delinquency and many crime correlates are the result of pleiotropic effects however at this time there isn t enough empirical research to provide definitive answers Genetic Polymorphisms and Antisocial Phenotypes Table 2 1 Dopaminergic polymorphisms o Dopamine is an excitatory neurotransmitter that activates postsynaptic dopamine receptors making an action potential more likely to occur in the postsynaptic neuron o Part of body s natural reward system Serotonergic polymorphisms o Serotonin is a neurotransmitter with inhibitory properties and the release of serotonin is thought to reduce innate drives regulate behaviors and control impulses o Two meta analysis studies reported strong evidence indicating that low serotonin levels have a significant role in a greater involvement in criminal and aggressive behaviors o Importantly the results also indicated the effect of serotonin was stronger and more consistent than were the effects of dopamine and norepinephrine Enzymatic breakdown polymorphisms o COMT metabolizes neurotransmitters such as dopamine epinephrine and norepinephrine o MAOA is one of the main enzymes responsible for breaking down neurotransmitters and more specifically MAOA is involved in the catabolism of monoamine neurotransmitters such as dopamine and serotonin Summary The process by which genes ultimately create proteins is known as the central dogma of molecular biology Alleles are alternative copies of genes A gene that consists of at least two alleles is known as a genetic Polygenic effects are the main way in which genetic variance produces polymorphism phenotypic variance phenotype Genes work in a probabilistic fashion where different alleles of a polymorphism can increase or decrease the odds of displaying a particular Genes that are involved in neurotransmission are among the most promising candidate genes for antisocial phenotypes COMT and MAOA are enzymes that breakdown neurotransmitters and terminate their activity Chapter 3 Gene X Environment Interactions At the heart of GxE lies that fact that all people have their own unique genotype and these unique genotypes produce different genetic predispositions o These predispositions in turn are responsible for creating differential susceptibilities to the same environments Formal definitions of GxEs the effect of the environment depends on the presence of genotype and the effect of genotype depends on the presence of the environment genotypes o Some genotypes are more sensitive to the environment than are other The results of adoption based studies have revealed that adoptees that have a biological parent who was arrested and an adoptive parent who was arrested are at greatest risk for becoming criminal The drawback to this line of research genetic risk is modeled as a latent factor meaning that we do not know the specific genes that are implicated in the GxE In the past decade research have moved away from modeling genetic risk as a latent factor and have begun to examine the effects that measured genetic polymorphisms have on behavioral phenotypes in the presence and absence of certain environmental stimuli Caspi and colleagues conducted the first study to detect a GxE between a measured gene and a measured environment on a behavioral phenotype o They hypothesized that a polymorphism in the promoter region of the MAOA gene the gene that produces the enzyme MAOA which breaks down neurotransmitters would affect susceptibility to childhood maltreatment It should be noted that not all research shows that genetic effects are more powerful in high risk as opposed to low risk environments o Ex Kevin Beaver et al study Other studies have also detected stronger genetic effects in low risk rather than high risk environments o One of the most common explanations to these seemingly counterintuitive findings is that high risk environments are so dominant that they can overshadow the effects that genes have on phenotypes Gene X Environment Correlations exposure to environments rGEs capture the processes by which genotype structures differential There is reason to believe that rGEs may be more common that GxEs Passive rGEs are the result of biological parents passing along genotype and an environment to their children Evocative rGEs arise from genotype eliciting certain reactions from the environment and these reactions are positively correlated with genetic predisposition o Genes influence the environment indirectly via phenotypes o Evocative rGEs probably can explain part of the reason why people with antisocial propensities tend to have difficulties