BEHAVIOR GENTEIC FINDINGS - Genetics 50%- Nonshared environment 40%- Shared environment 10% there is nothing anti-sociological about BG methods in fact, BG methods are the most reliable way to estimate environmental effects- allows us to directly and accurately estimate environmental influences on a given phenotype- differentiates between shared and nonshared environmental influences how do we estimate these effects? most researchers (including criminologists) look at only one child per family- can’t separate genetic from environmental influences need to look at more than one child per family Twin-based design is the most common technique- Natural Experiment Why?- we can compare monozygotic twins (MZ) to dizygotic twins (DZ) * MZ twins = identical twins * DZ twins = fraternal twins TWIN STUDIES based a fairly assumption- if MZ twins are more similar to each other than DZ twins, then genes have great influence what else could account for this finding? why not the shared environment?* If DZ twins are just as similar to one another as MZ twins, then the environment has a greater influence MZ twins share the same environment DZ twins share the same environment The only reason that MZ twins would be more similar to another would be because the share twice as much genetic materialCRITICISMS OF TWIN STUDIES critics of twin based research have argued that there are serious limitations of the twin-based design- argue that these limitations result in artificially inflated h2 estimates- also result in artificially deflated C2 and E2 estimates 1. Violationof the equal environments assumption (EEA)- MZ twins share environment that are more similar than DZ twins since they are genetically identical2. Presence of assortative mating- mates seek out other mates with genomes that are similar to their own- results in DZ twins that may share more than 50 of their dissenting DNAResponses to criticisms Violation of the EEA- studies have examined misclassified MZ/DZ twin pairse.g., classified as a Dz pair, but is actually an Mz pairMz(Mz) Dz(Mz) Mz(Dz) Dz(Dz)- No support for inflated estimates of h2 assortative mating- studies have found support for assortative mating- increases the genetics similarity between non-M2 siblings- works to decrease estimates of h2 not increase them*only artificially deflated(2/18/14) Other BG Techniques limitations not a concern- additional techniques have been developed anyways researchers have developed additional methods to separate genetic & environment influences:1. Adoption studies2. Mz twins separated at birth (MzA)3. Family StudiesAdoption Studies- we can estimate h2, c2, and e2 with adoption studies (we don’t just need to twins)- we can compare the adoptees with their biological parents and with their adopted parents- If the adoptee more closely resembles their biological parents, then genes influences the examined phenotype- If the adoptee more closely resembles the adopted parents, then the environment has a stranger influenceon the examined phenotypeM2 Twins separated at birth  we can also examine Mz twins who were separated at birth (MzA)- these are rare samples but some studies have identified an impressive number of MzA twins any resemblance between them would be due to genetics- no share environment- remember that nonshare environments make siblings different from one another (ex shows such as sister sister, parent trap)Family Studies logic of MZ twin-based design can be extended to other family members as well  most common use is with non-twin sibling pairs- full sibling, half sibling, cousin, etc also possible with biological parentsShare genes 1: parents = 50%Full siblings = 50%Half siblings = 25%Cousins= 12%- use parents score on the phenotype of interest as a “gross” genetic measure- possible anytime we compared at least 2 people from the same householdSibling Type Level genetic relation A/C genetic riskMz 1.00 5Dz .50 4Full sibling .50 4Half sibling .25 3cousins .125 2* need to know the level of genetic relatednessFINDING FROM BG what do BG studies reveal about the heritability of behavior and personality traits?- findings are relatively consistent across different methodologies- indicates that the results from any one method are valid and reliable most behaviors & personality traits are highly heritable (.50-.90)- .50 represents a proportion & can be converted 2 a percentage (50%)- The shared environment has very little effect- The non shared environment is important- Findings are so robust they have been developed into formally written laws3 Laws of Behavior1. First law: All human behavioral traits are heritable.2. Second law: The effect of being raised in the same family is smaller than the effect of genes3. Third law: A substantial portion of the variation in complex human behavior traits is not accounted for by the effects of genes or familiesBehavior Genetics BG methods provide us with a good starting point Don’t provide much detail- what genes are influencing the phenotype?- what environments are influencing the phenotype? genes that are responsible for the development of problem behaviors and traits(2/20/14) GenesIntroduction to Genetics- There are approximately 25,000 genes in the human body- Genes are stretches of DNA that work together to perform specialized functions- To better understand genes, we need to discuss DNA- DNA is a chemical code that allows us to form, develop, and function- DNA is stored in the nucleus of every cell except red blood cells- information encoded into DNA determines virtually every observable and many unobservable characteristics- one of the reasons that people are different is because their DNA varies- every person has their own unique sequence of DNA (except M2)- each person’s arrangement of genes is referred to as a genotype The structure of DNA- 2 fibers twisted around each other to form a double helix- each fiber is referred to as a polynucleotide- along the backbone of each polynucleotide is a sequence of nucleotides (also called bases) There are four different types of bases1. Ademine (A)2. Thymine (T)3. Cytosine (C)4. Guanine (G) The four bases (nucleotides) make up the genetic alphabet How are the two polynucleotides held together? through bonds between the bases- ‘A’ only pairs with ‘T’- ‘G’ only pairs with ‘C’ These bonds hold the two strands of DNA