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Regulating Gene Expression Exams back T 9/30 Bonus #1 is due 10/02 What makes us who we are? Nature and Nurture Based on “Nature via Nurture” by Matt Ridley (2003) Genes Traits Genes code for proteins. These proteins give rise to traits… Genes Traits Genes code for proteins. These proteins give rise to traits… It is rarely this simple. Imprinting: exposure to movement (environment) sets “mother” X/Y chromosomes in humans: genes = traits This article, shows how even today people see nature and nurture as opposing each other: The Pathogenesis of the Glaucomas: Nature versus Nurture Mackey, et al., Clinical & Experimental Opthamology vol 36, pg 297, April 2008 Twin studies have been used to determine the heritability of various traits. Types of twins: http://pennhealth.com/health_info/pregnancy/000199.htm Twin studies have been used to determine the heritability of various traits, but there are some caveats: How many twins have been studied? How different are the environments? Correlation of weight and relatedness Correlation of weight (BMI) % Identical twins reared together 80 Identical twins reared apart 72 Fraternal twins reared together 43 Biological siblings 34 Parents and children living together 26 Adopted children and parents 4 Unrelated children living together 1 *But food preference shows little genetic correlation The nature of environmental influences on weight and obesity: A behavior genetic analysis. Grilo, Carlos M.; Pogue-Geile, Michael F.; Psychological Bulletin, Vol 110(3), Nov 1991. pp. 520-537. And two books by Matt Ridley: Nature via Nurture (2003) and Genome: the Autobiography of a Species in 23 Chapters (1999) Intelligence Correlation of IQ Inheritance : The same person tested twice Identical twins reared together Identical twins reared apart Fraternal twins reared together Biological siblings Parents and children living together Parents and children living apart Adopted children living together Unrelated people living apart % 87 86 76 55 47 40 31 0 0 From two books by Matt Ridley: Nature via Nurture (2003) and Genome: the Autobiography of a Species in 23 Chapters (1999) When the environment is equal (everyone has access to resources), genetic differences are magnified. When environments are different (only a few have access to resources), environmental differences are magnified. Proof or disproof? Correlation of IQ Inheritance : The same person tested twice Identical twins reared together Identical twins reared apart Fraternal twins reared together Biological siblings Parents and children living together Parents and children living apart Adopted children living together Unrelated people living apart % 87 86 76 55 47 40 31 0 0 From two books by Matt Ridley: Nature via Nurture (2003) and Genome: the Autobiography of a Species in 23 Chapters (1999) Can we see a genetic basis for complex behaviors? Voles Prairie Montane • Monogamous • Nonmonogamous • Both parents care • Mother cares for for young young briefly Oxytocin and Vasopressin (hormones) Water/salt balance Contraction of womb and milk production Encourages bonding between individuals Hormones are molecules produced in one cell and signal another. Oxytocin and Vasopressin (hormones) Water/salt balance Contraction of womb and milk production Encourages bonding between individuals Voles Prairie Montane • Monogamous • Nonmonogamous • Both parents care • Mother cares for for young young briefly Voles Prairie • Monogamous • Both parents care for young Montane • Nonmonogamous • Mother cares for young briefly Same levels of oxytocin and vasopressin Hormones are molecules produced in one cell and signal another. Voles Prairie • Monogamous • Both parents care for young Montane • Nonmonogamous • Mother cares for young briefly Same levels of oxytocin and vasopressin • More receptors • Less receptors Voles Prairie Montane • Monogamous • Nonmonogamous • Both parents care • Mother cares for for young young briefly Same levels of oxytocin and vasopressin • More receptors • Less receptors Inject hormone into brain •? • ? Voles Prairie Montane • Monogamous • Nonmonogamous • Both parents care • Mother cares for for young young briefly Same levels of oxytocin and vasopressin • More receptors • Less receptors Inject hormone into brain • Monogamous • Nonmonogamous Voles Prairie Montane • Monogamous • Nonmonogamous • Both parents care • Mother cares for for young young briefly Same levels of oxytocin and vasopressin • More oxytocin • Less oxytocin receptors receptors Block receptors •? • ? Voles Prairie Montane • Monogamous • Nonmonogamous • Both parents care • Mother cares for for young young briefly Same levels of oxytocin and vasopressin • More oxytocin • Less oxytocin receptors receptors Block receptors • Nonmonogamous • Nonmonogamous Voles Prairie • Monogamous • Both parents care for young Montane • Nonmonogamous • Mother cares for young briefly Same levels of oxytocin and vasopressin • More oxytocin • Less oxytocin receptors receptors Increase levels of receptors (genetically) in ventral pallidum • Monogamous • Monogamous Voles Prairie • Monogamous • Both parents care for young Montane • Nonmonogamous • Mother cares for young briefly Same levels of oxytocin and vasopressin • More receptors • Less receptors Why might these voles use different reproductive strategies? Prairie voles Montane voles • Monogamous • Nonmonogamous • Both parents care • Mother cares for for young young briefly Why might these voles use different reproductive strategies? Prairie voles: Montane voles: Resource poor Resource rich habitat habitat • Monogamous • Nonmonogamous • Both parents care • Mother cares for for young young briefly We looked at the mechanisms of gene expression, now we will look at its regulation. Combinations of 3 nucleotides code for each 1 amino acid in a protein. Exons are a very small part of DNA Fig 15.1 Each step in gene expression presents an opportunity to regulate when and how much of a gene product will be produced. Fig 15.1 Why change gene expression? •Different cells need different components •Responding to the environment •Replacement of damaged/worn-out parts Two points to keep in mind: 1. Cellular components are constantly turnedover. 2. Gene expression takes time: Typically more than an hour from DNA to protein. Most rapidly 15 minutes. Fig 15.1 Blood clotting must happen within minutes mRNA levels change in response to cold acclimation Fowler and Thomashow The Plant Cell, Vol. 14, 1675-1690, 2002 DNA damage inhibits rRNA transciption Fig 1b The ATM repair pathway inhibits RNA polymerase I transcription in response to chromosome breaks Nature Vol 447 pg 730-734 (7 June 2007) •Gene expression can be controlled at many points between DNA and making the final proteins. •Changes in the various steps of gene expression control when and how much of a product are produced. Fig 15.1