2. Today
• Quiz 3 review
• Course evaluations
• Vilain lecture material from week 9
• Saguy – review of sociology readings
3. 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
4. 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
5. 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
6. 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
7. Looking for “a” gene
• Candidate genes
• Best guess for a gene is nominated and then
studied
8. 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
9. 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
10. 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
11. 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%
12. 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
13. The ex-gay movement
•1. History of Mental Health Attitudes toward
Homosexuality
•2. Sexual Conversion Therapies in a Cultural
Context
•3. Clinical/Research Issues
14. History Of Mental Attitudes
•19th: From Sin to Sick
• - from judgment to “science”: ex. Degeneracy theory “arrested
development” (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
15. “Conversion”/”Reparative”
Therapy in Context
- Normalization Provokes Culture wars
-Opposing Views on Homosexuality:
-Normal/Identity Model: accepting one's normal
homosexual orientation
-Illness/Behavior Model: rejection of identity model
and says it is abnormal
16. 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
17. Gay Rights, Research, and Politics
• Research about the origins or sexual orientation
is 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.
18. Saguy exercise
• Race Covering Flaunting
• Sex Appearance
• Motherhood
• Class Affiliation
• Fat
Activism
• Others
Association