Sex chromosomesKlinefelter's Syndrome- XXYSuper male– XYYTurner's Syndrome - XOTriple X– XXX–Know percent of genetic relatedness among parent/child, sibs, grandparents, etc. (lecture). –Genetic Relatedness–Child to Parent 50%–Siblings 50% (average)–Grandchild to grandparent 25%–Identical twin 100% (monozygotic)–Fraternal twins 50% (dizygotic)–Know Gotlieb’s Epigenetic Theory (lecture, also p. 56). –Epigenetic (Ethological) TheoryGenes(& their products) interact with the environmentto guide development.Genes & environment are partnersin directing organisms - they co-act.Genetic endowmentMakes outcomes/paths probableEnvironmental factorsCan influence genes and genetic outcomesGenes and environment are partners in directing organisms, they co-act–Define epigenetics.Epigenetics involves changes in structures associated with chromosomes& DNA that affect gene expression without altering DNA sequence.–Know the two mechanisms discussed in class: histone acetylation and DNA methylation (lecture & p. 86). - DNA strands roll over nucleosomes, which are a cluster of nine histone proteins, to form a chromosome.- Acetyl groups attached to the histones can affect the accessibility of the DNA.- Acetylationof histone proteins reduces the affinity between histones and DNA. RNA polymerase and transcription factors then have easier to access the DNA. Therefore, in most cases, -histone acetylation enhances transcription-histone deacetylation represses transcription.DNA methylation is the addition of a methyl group (CH3)directly to the DNA's cytosine base. - It may affect gene transcription through several different mechanisms (usually repression of transcription). - The methylation pattern is heritableafter cell division. Therefore, DNA methylation plays an important role in ell differentiation during developmentExamples:-Methylated DNA or histones that persistRestraint stress in ratsChronic social defeat in rats
Depression in humans-maternal traumatic eventLowered cortisol levels in mothers and in off-spring of mothers pregnant at WTC 9/11/2001, esp. 3rdtrimester–What is behavioral genetics (p. 54)? -The field that seeks to discover the influence of heredity and eviroment on individual differences in human traits and developement–Define and distinguish the different genotype/environment correlations: passive, evocative, & active andshow how the relative importance of the three types of interactions may change with age (p. 54-57). PassiveCorrelations that exist when the biological parents, who are genetically related to the child, provide a rearing environment for the childEvocativeCorrelations that exist when the child’s characteristics elicit types of environmentsActive (niche-picking)Correlations that exist when children seek out environments they find compatible and stimulating–Prenatal diagnostic tests: ultrasound, amniocentesis, chorionic villus sampling (CVS), maternal blood sampling & PGD and sex determination (p. 62-63)?