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33 Cards in this Set
- Front
- Back
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Vilain's central research question
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is homosexuality determined by biological or environmental factors?
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most subjective part of research
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what actually to study
what's worth empirical research |
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human model- pros
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directly relevant to question, highly significant
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human model- cons
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pheno difficult to define
limited access to relevant tissue (ex- brain)...molecular mechanism can't be examined ethical concerns |
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animal model- pros
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phenotype easier to measure, relevant tissue accessible
*can do experiments, see molecular mechanisms |
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animal model- cons
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may not be directly relevant to humans
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issues with recruitment of subjects
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-selection bias (representative sample?)
-phenotypic definition (how to define homo.) -biological material (which tissue, what time of development) |
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different types of experimental design (3)
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1. linkage studies
2. association studies 3. expression studies |
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defining sexual orientation in humans vs. animals
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humans -identity
sexual attraction behavior animals- easier to measure behavior |
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linkage analysis
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analysis of family genomes- co segregation
-search for genetic region passed on to affected members more than non-affected -need more than 1 affected person *VERY EFFICIENT |
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problem with linkage analysis
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sexual orientation as a trait is waay more complicated, ill-defined, not caused by one gene
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association studies
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random ppl in population, look @ genetic markers shared amongst ppl with common trait
*need large group of ppl w/ trait, group of demographically closely matched controls **start with candidate genes |
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problem with association studies
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need 1,000s of ppl, hella $$$
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expression studies
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look at certain tissue, see if particular gene is turned on/off
**start with candidate genes (tell you which genes matter) |
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epigenetics
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genes in combination with specific environment
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genetic imprinting
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imprinted genes expressed from only 1 chromosome depending on if maternally or paternally inherited
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paternal alleles can...
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stimulate embryonic growth
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maternal alleles can...
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inhibit embryonic growth
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gene expressed if...
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next to unmethylated cytosine
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gene not expressed if...
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next to methylated cytosine
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DNA METHYLATION
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regulates gene expression
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problem with epidemiological measures of environment
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difficult to estimate objectively the duration, intensity of environmental influences
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twin studies
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-have entirely same genome, not all the same traits (can determine effects of environment)
*diff epigenetic expression *concordance rate should be higher in mono than dizygotic twins |
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co-segregation (linkage analysis)
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genetic marker tends to go along with certain trait
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xq28
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4/5 times they found a link to male homosexuality
(x-chrom, passed down from mother) |
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linkage and association study
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what genes people have
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gene expression study
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what genes ppl are actually expressing
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gene expression and gay rams
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no differences in gene expression btwn gay and straight rams
-maybe has nothing to do with genes -maybe should look at gene expression during development, not adulthood -what regions of brain to study |
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10q26 allele
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from father- no more gay than predicted by chance alone
from mother- more often gay than predicted by chance alone |
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not whether or not you get the gene, but...
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who you get it from determines whether the gene gets turned on or off (epigenetics)
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mouse pups being licked by mom
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changes how genes expressed later in life- changes in gene expression can be passed on to offspring
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concordance rate in monozygotic twins
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52%
(not all explained by genetics) |
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new Vilain twin study
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discordant twins (separated strait from gay)
*only differed by 4% |
