NE102 Lecture Notes 3

New alleles arise via various errors of dna

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evolution is occurring.  New alleles arise via various errors of DNA replication in germ-like cells (sperm and  eggs) Mutations Consequences of mutations for organism’s phenotype depend on where the mutation  occurs Evolution does not occur only when new proteins structures arise – changes in gene  regulation are vey important Ex.) Evolution of lactose tolerance in adult humans – same enzyme (lactase), but  altered temporal expression pattern (lactase is expressed throughout adulthood).  Analogy of the  genetic toolkit  – evolution can occur by the redeployment of existing  genes in new contexts via regulatory changes Mutations in coding or regulatory regions likely to often be deleterious, so natural  selection should eliminate most variation in these regions (they are  conserved -  similar). 
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NE101 Recap – “Integrative Biology” 18:04 Mutations in noncoding regions likely to be neutral, so should accumulate over time.  Some regions with critical functions in all/most organisms have evolved very little over  billions of years – they are highly conserved.  Gene for small ribosomal subunit BLACK BOX #2: DEVELOPING NEURONS Development  refers to the growth and maturation of individual organisms within their  lifespans (a single generation) Induction by growth factors and other signaling molecules QUESTION: How do signaling molecules induce differentiation?  Neurons “compete” for neurotrophic factors a.1. Neurons take up neurotrophins and transport them to soma a.2. Neurotrophins regulate gene expression a.3. Neurons that take up too few neurotrophins undergo apoptosis Neurotrophic factors (neurotrophins) are cell signaling molecules (P.S. – NGF is one!) What’s the deal with NGF? How can it have so many functions? Same signaling molecules can engage multiple different intracellular signaling pathways BLACK BOX #3: PATTERNING The expression of developmental patterning genes is highly conserved in animal brains. Gene expression refers to the patter of WHEN and WHERE genes are “turned on” or  “turned off” Ex.) Pax6 Hox genes are the most well-known patterning genes. 
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NE101 Recap – “Integrative Biology” 18:04 Determine anterio-posterior patterning.  QUESTION: What controls when/where patterning genes are expressed (including at  the very beginning of development)? Development from identical precursors to different body regions with differentiated cell  and tissue types is mediated by cascades of gene regulation.  EXAMPLE: Fruit flies (drosophila melanogaster)  Model system where body patterning well understood What are the regulatory cascades that lead a tiny, undifferentiated embryo to develop  into a complex adult?
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  • Spring '13
  • KenAdams
  • AP, NGF, map kinase, extracellular signaling molecules

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