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3 Naturenurture3



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  • 1. The Nature part of nature/nurture for learning
    • A gene is a part of a chromosome. Genes are in pairs
    • Genes affect our learning ability
    • A chromosome consists of a double-stranded chemical = DNA
    • Each pair (23 in humans) splits apart taking its genes with it
    • Sometimes can get the genes from the other chromosome by a process called `crossing over’
    • Natural selection is not good or bad.
    • It just happens.
    • Most of the mutations that occur are deleterious.
  • 2. Darwin exploring
  • 3. Evolution of traits
  • 4. Natural selection (Natura)
  • 5. There was probably one ancestor from one place- Africa.
    • All modern people can trace their heritage to Africa.
      • DNA samples of 12,127 men from 163 Asian and Oceanic populations.
      • Every one of the subjects carried a mutation at one of 3 genetic markers on the Y Chromosome.
        • Those three sites can be traced back to a single African population some 35,000 to 89,000 years ago.
    • Although there was probably one population, several species of early man may have appeared and died out.
    • Somewhere between 200,000-500,000 years ago some migrated out of Africa (Lemonick, 1994; Harris and Hey, 1999).
  • 6. All children from the same mother have identical mitochrondrial DNA
    • Africa has been shown to be the actual birthplace of Eve at 200,000 years ago on the basis of mtDNA (Cann, Stoneking, and Wilson)
    • mtDNA change only by mutation (1-2% every 100,000 years).
    • Each chance mutation is preserved in the next generation
  • 7. 50 genes =cognitive differences between man and ape.
    • Just 50 out of 140,000 genes that humans and chimps are thought to possess ( 0.3%) may account for all of the cognitive differences between man and ape.
      • Chimps and gorilla are more closely related to humans than they are to orangutans (Jean-Jacques Hublin)
  • 8. Humans = a third race of chimpanzees.
    • From our DNA , humans appear from a genetic perspective as a third race of chimpanzees.
    • Although chimps took a different evolutionary path from humans about 8 (9?)? million years ago, they share 98.4 percent of our DNA.
    • In comparison, on the average humans share 99.8 percent of the same genetic material (Lewontin, 1972).
  • 9. There are Learning and memory genes
    • during learning (STM) and memory (LTM) new genes are expressed that are required to establish long-term memories.
    • There are specific genes devoted to memory storage.
      • most identified as affecting memory are involved in signal-transduction pathways for purposes unrelated to memory
  • 10. Evolution of Gene Related to Brain's Growth
    • Genes affect the evolution of the cortex.
    • A gene (ASPM) helps determine the size of the human brain.
      • ASPM has been under intense Darwinian pressure in the last few million years,
      • changed its structure 15 times since humans and chimps separated from their common ancestor.
  • 11. Formation of memories
    • If neuron fires often and strongly it is declaring that this is an event that should be recorded and the relevant genes turn on.
    • The synapses holding STM are made by proteins and become tatooed into LTM.
  • 12. LTM (long-term memory)
    • Long-term strengthening of synaptic connections involves
      • the induction of new genes in the neuron
      • an increase in the number of functional synapses
  • 13. Genes know when to strengthen a synapse. Genes manufacture synapse-strengthening proteins. The cell’s nucleus “listens” to the cell’s action potential to determine when to strengthen a synapse and make a memory last.
  • 14. CREB is turned on by genes and vice versa
    • CREB= a molecular switch for the formation of LTM.
    • CREB is required for the stability of initial and reactivated memories.
  • 15. Gene zif268 is associated with learning and memory.
    • It is turned on by hippocampal neuron firing.
    • When the membrane depolarizes the machinery in the nucleus listens to the output of the neuron to decide whether to synthesize memory-fixing proteins.
  • 16. Turn on active Genes genes
  • 17. knockout-mouse or fly (Drosphilia)
    • tells us what genes are necessary to develop a normal learning and memory phenotype in the adult.
    • These knockout lines do not give us access to all the molecules in the adult brain that participate in memory encoding.
    • Knockout fly used in experiment in next movie clip.
  • 18. Master genes rule cascade of genes genes1
  • 19. Learning genes in Drosphilia
    • 4 mutants obtained from behavioral screens: dunce , rutabaga , amnesiac and linotte .
      • (3 of the 4 mutants affect molecules that are involved in learning).
    • the mutant dunce seemed to affect learning the most
  • 20. Environmental modification of heritable behaviors (nature + nurture)
    • Nature: Different Genetic strains of mice
    • bred to be smart.
      • in an elevated maze.
      • swimming (Japan conf).
    • Nature + Nurture : Phenylketonuria (PKU)- genetic inability to metabolize amino acid phenylalanine.
      • Can lead to retardation.
      • Can control by diet.
  • 21. Nurture: environmental enrichment
    • improved performance of rats in a water maze
    • tended to increase activity of CREB in the hippocampus.
  • 22. Nurture Deficient folate = cognitive impairment.
    • children born to severely folate-deficient mothers often have abnormal or delayed intellectual development.
    • taking adequate folate during pregnancy has been proven to cut nervous system birth defects by 50%.
    • low folate - associated with depression + dementia in the elderly.
  • 23. Neuron on right from animal in stimulating environment=more branches
  • 24. AT BIRTH 3 MONTHS 2 YEARS Can either enhance or retard the normal development of the brain by the type of environment
  • 25. Thymidine study The development of the brain as shown by splitting and migration of DNA
  • 26. My research using the DNA in our genes to look at how our brain develops.
    • Pick a more primitive species.
    • Look at parts of the new brain= the thalamus and neocortex.
    • Those are what is important for higher processes such as learning.
  • 27. monodelphis opossum= short tailed gray opossum= Brazilian opossum
    • Use of a marsupial, the monodelphis opossum.
    • This allows us to insert Thymidine in the embryo.
  • 28. Development of the thalamus in gray short-tailed opposum (J. of Mammalogy).
    • Advantage of development in a marsupial= the embryos can received direct injections.
  • 29. Thymidine
    • Thymidine is taken up in the DNA `mother cells’.
    • They split into `daughter cells’ (with half as much DNA) etc.
    • The daughter cells and granddaughter cells migrate to their final place of work.
  • 30. Tritiated Thymidine
    • The Thymidine is radioactive and so can be detected by its reactivity on an emulsion coat put over the brain tissue (which is mounted on a slide).
  • 31. Tritiated thymidine was injected into the monodelphis domestica at embryonic ages -3 through day +16.
  • 32. Plotting for documentation of location
    • My job is to document the location within the brain of the mother cells, daughter cells etc.
    • I focused on the thalamus which is the central place for all of the information either going to the cortex or descending from the cortex= It is critical for all cortical activity.
  • 33. Purpose of the study
    • From this work we learn about how the brain develops.
    • There are critical periods where the brain is more susceptible to damage. These would be more prevalent in the period before the neurons have migrated to their final position.
  • 34. results The thalamus Develops at the Same time as The cortex. Cortex Same as the brainstem In that way. Easier to Repair?
  • 35. Stem cell research
    • This work can help with stem cell research studies.
    • Tissue that is not yet fully differentiated is more likely to be able to become another part of brain tissue.
    • Someday brain repair or partial brain transplants may be a possibility for humans.
  • 36. Stem cells (1)
  • 37.
    • See you next time