Unformatted text preview:

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

View Full Document


Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...

Join to view BEHAVIOR GENTEIC FINDINGS and access 3M+ class-specific study document.

We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view BEHAVIOR GENTEIC FINDINGS 2 2 and access 3M+ class-specific study document.


By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?