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Kog.Neuro. (Fach) / Genes to Behaviour (Lektion)

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• How to study the heritability of psychological traits? Twin studies! look at the difference between dizygotic and monozygotic twins in terms of genotype and phenotype
• Which psychological traits are heritable? -general intelligence (.52)! -also: verbal reasoning, processing speed, scholastic achievement, spatial reasoning, extraversion, vocational interests (.42), ... memory (.22)
• Heritability of psychological disorders schizophrenia (.8)...major depressive disorder (.4)
• Pleiotropy one genotype influences many phenotypes (one-to-many-relationship)
• Polygenicity One phenotype is influenced by many genotypes (many-to-one-relationship)
• Many-to-many-relationship many genotypes influence many phenotypes !
• What does polygenicity mean in terms of gene expresssion? When there is polygenicity (many genotypes influence one phenotype), there is a slightly higher probability of gene expression. But no genetic determinism.
• How is a gene expressed? genome (DNA), consisting of CGTA, is transformed into the transcriptome (RNA), which is then translated (via mRNA, into polypeptides) into the proteome (proteins!), which are crucial for differentiation for neural circuits, nerve cells, therefore influence the behaviour! genome -> transcriptome -> proteome -> neurome -> phenome !
• How do genes (and their proteine products) determine brain structure? -> genes code for proteins (via transcriptome) -> expressed genes in the brain are important for development, regulation and maintenance of neural circuits -> many gene products are important for differentiation of a single nerve cell, and many more for a neurocircuit !
• genetic polymorphism = more than one allele carries the gene's locus 
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• different types of genotype (-> genetic polymorphism) genotype: homocygote or heterocygote
• single-nucleotide polymorphism variation in a single nucleotide (codon = 3 bases code for one aminoacid) lead to the transcription of a different aminoacid -> proteine -> variation in dna can lead to a different transcriptome and proteome
• Experience can modify brain structure - do you know experiments accounting for this phenomenon? What is a problem of this argumentation? => london taxi driver experiment -> taxi drivers had a smaller anterior, and a larger posterior part of the hippocampus (both left and right hemisphere)! => musicians -> what came first - chicken or egg? 
• Social Phobia - Psychotherapy vs Pharmacotherapy -> PET scan before and after 9 weeks treatment -> reduced symptoms and reduced regional Cerebral Blood Flow (rCBF) in the same brain areas (eg amygdala and hippocampus)  => experience can alter brain structure
• Examples for chromosome inactivation (=silencing) x-chromosome inactivation in females -> transcriptional silencing -> via epigenetic processes -> dna methylation also: tortoiseshell cat is always female 
• parental imprinting , example! a single allele is differentially expressed, depending on the sex of the transmitting parent -> example Angelman-syndrome (maternal), Prader-Willi-syndrome (paternal)
• anxiety disorder bei Kids responder vs non-responder, significant changes in DNA methylation => responder significant increase in DNA methylation, non-responder significant decrease in DNA methylation
• trans- and multigenerational inheritance -> gene x environment interaction (Mice!) "Good" and "Bad" Mother -> low-licking and high-licking behaviour Kids will be not fearful or fearful When Kids are raised by other mother -> kids of good mother raised by bad mother become slightly fearful , while kids of bad mother raised by good mother are not fearful => Stress hormone receptor silenced by epigenetic mechanism!
• evocative gene-environment correlation individuals inherited behaviour evoked a specific environmental response
• active gene-environment correlatoin individual possesses the inherited disposition to seek out specific environments, which in turn influence him or her in a specific way
• gene x environment interaction different genotypes respond to environmental variation in different ways

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