Section 10
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Section 10






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    Section 10 Section 10 Presentation Transcript

    • Section 10 3/13/13
    • Today• Quiz 3 review• Course evaluations• Vilain lecture material from week 9• Saguy – review of sociology readings
    • Difficulties in studying biological contribution to homosexuality• Some studies on humans are neither practical nor ethical• Animal models may not be optimal because of human/animal differences• Recruitment difficulties – Selection bias – How is homosexuality defined? – What is the object of study? Tissue? Genes? An area of the brain? During what period of development?• Gene environment interactions
    • Looking for “a” gene• Linkage analysis: don’t know which specific genes are responsible – Narrowing it down: whichever parts of the genome are shared between affected family members – Need 2+ affected family members• Identify family members with the same trait. Find the genetic marker for that trait• Repeat the process multiple times to identify a genetic marker that is statistically more linked to a particular trait• In other words, search for a genetic region that is passed on to affected members in a family more than to those not affected
    • Linkage analyses• Suggests Xq28 – This region is on the tip of the X chromosome• However, linkage studies suggest other autosomal regions (not on sex chromosomes)• Could be more than one gene and multiple physiological determinants/factors• 12 million base pairs in human DNA makes the search challenging
    • Looking for “a” gene• Association study: similar to linkage, but in larger populations. (Xq28 region = many alleles) – E.g.: Are gay people much more (or less) likely to have a specific allele than straight people?• Search for a genetic marker that is shared amongst people with a common trait. Requires (1) a large group of individuals with the trait and (2) a comparison to a large group of closely matched controls• Families not required
    • Looking for “a” gene• Candidate genes• Best guess for a gene is nominated and then studied
    • Looking for “a” gene• Gene expression• Examine microarrays, comparing heterosexual and homosexual individuals (sheep in this case)• Do some genes show signs of stronger expression in the phenotype?• Gene expression in brain regions compared – null results
    • Epigenetics• Gene expression varies and can be regulated by methylation• Methylation acts on cytosine• Epigenome seen as interface between environmental signals and persistent behavior• But it is currently impossible to determine “how much” environmental influence
    • Epigenetics continued• Can be viewed as “a unifying solution for gene-environment interactions”• Only have to look for methylation – not the cause of methylation• In addition, it can also be assumed that there will not be a one-to-one correlation between the presence of a particular allele combination and homosexuality• Therefore, twin studies may be useful
    • Twin studies• Because while MZ twins share 100% of their DNA, they do not have the same epigenetic patterns• Recall concordance rates for male homosexuals: – MZ = 52% – DZ = 22%
    • Twin studies• Looking at some of the regions of the genome identified by linkage analysis• Looked for differences between the methylation of these genes between twins• 4-5% differences in methylation
    • The ex-gay movement•1. History of Mental Health Attitudes towardHomosexuality•2. Sexual Conversion Therapies in a CulturalContext•3. Clinical/Research Issues
    • History Of Mental Attitudes•19th: From Sin to Sick• - from judgment to “science”: ex. Degeneracy theory  “arresteddevelopment” (Freud)•Mid 20th: DSM : efforts to standardize mental health in general• -1952: Sociopathic Personality Disturbance• -1953: Evelyn Hooker – major evidence to the contrary• -1973: APA Decision to remove homosexuality• Interaction with culture/politics: i.e. activism informed the APA• not a mental illness  “normalization”  cultural war
    • “Conversion”/”Reparative” Therapy in Context- Normalization Provokes Culture wars-Opposing Views on Homosexuality:-Normal/Identity Model: accepting ones normalhomosexual orientation-Illness/Behavior Model: rejection of identity modeland says it is abnormal
    • Clinical and Research Issues•- Robert L. Spitzer: Reparative Therapy Works [?] – Scales of sexual orientation: •attraction, identity, sexual behavior• Critiques: –no follow-up or face to face interviews –retrospective accounts –recruitment and sample bias –NO peer review
    • Gay Rights, Research, and Politics• Research about the origins or sexual orientationis tied up in politics. – Anti-gay activists use “reparative” therapy as evidence that sexual orientation is “changeable” and a “choice” and thus not deserving of legal rights and protections. – This stance is used to justify legal discrimination in employment, marriage rights, and other areas.
    • Saguy exercise• Race Covering Flaunting• Sex Appearance• Motherhood• Class Affiliation• Fat Activism• Others Association