Developmental Psychobiology

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Developmental Psychobiology

• The role of genes in development

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Two Views of the gene

• Preformationist
• Probabilistic Epigenetic

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Preformationist Perspective

• Derived from the homunculi concept
• Reductionist orientation
• Views genes as distinct entities - nouns
  contributing independent sources of variance
• Gene Environment interactions viewed from a
  reaction range perspective.

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Probabilistic Epigenetic

• Genes are part of an integrated developmental
  system critical yes, but just one participatory
  factor
• Non-reductionistic.
• Recognize genes as verbs, more of a process
  than an entity
• Gene environment transactions viewed from a
  norm-of-reaction perspective

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A tale of two-sciences

• Quantitative Behavioral Genetics
• Developmental Psychobiology

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Quantitative Behavioral Genetics

• Stems from a preformationist perspective
• Based on methodological approach developed by
  Francis Galton
• Statistical attempt to account for Mendels
  observations.
• Developed notion of the hypothetical gene

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The hypothetical gene

• Concept of a gene predated discovery of DNA
• Idea of Gene as a blue-print that carried
  developmental information came prior to molecular
  genetics.
• Led to central dogma of genetics

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Central Dogma of Genetics

• DNA
• RNA
• Protein

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Behavior Genetic Extension

• Genotype
• Neural endophenotype
• Behavioral Phenotype

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Twin Method Logic

• P h2 c2 e2
• h2 2(rmz rdz)
• c2 rmz h2
• e2 1 h2 c2

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Quantitative Behavioral Genetics

• A Science without data

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What Genes Are

• Genes are made up of DNAthe complex protein code
  of genetic information
• DNA directs the form and function of each body
  cell as it develops

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What have we learned

• Not all nucleotide sequences code for proteins
• Same nucleotide sequence codes for multiple
  proteins
• Limited complexity of human genome 30,000 genes
• Difference between P-genes and D-genes
• Interdependency of genetic transcription with
  development

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Probabilistic Epigenesis revisited

• Protein synthesis as a function of vertical and
  horizontal co-actions
• Norm-of-Reaction Concept
• Behavioral Canalization
• Neophenotypes

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Horizontal Co-Actions

• Gene to Gene regulatory networks

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Vertical Co-Actions
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Hierarchy of Reciprocal Influences
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Norm of Reaction Concept
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Canalization
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Key Developmental Principles

• Probabilistic Epigenesis
• Integrative Levels
• Complex Adaptive Systems
• Self-Organization
• Emergence
• Spontaneous Symmetry Breaking

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The Role of Genes in Development According to
Probabilistic Epigenesis
Cellular Context
DNA
RNA
Protein
DNA
RNA
Protein
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What is a Complex System

• Complex systems theory attempt to understand how
  collective behaviors of systems arise from the
  complex interactions of the systems parts.
• Protiens --gtAmino Acids
• Brains --gtNeurons
• Organisms --gtGroups
• Groups --gtCulture

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A Bio-Psycho-Social Model
Relating Risk and Mechanisms of Alcohol
Teratogenesis
Abel Hannigan (1995)
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Spontaneous Symmetry Breaking

• Formation of Pattern due to heterogeneity in long
  range spatial correlations

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Formation of Neural Tube

• Three primordial tissues
• endoderm
• mesoderm
• ectoderm
• Which tissue does nervous system develop from?
• ectoderm

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Neural crest
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Neural crest
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Key Developmental Processes

• Fate Maps
• Asymmetric Cell Division
• Induction
• Developmental Genomics
• Cell Competence
• Genetic Redundancy
• Positional Information
• Differential Determination
• Lateral Inhibition
• Genetic Networks

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Key Developmental Processes

• Fate Maps
• Asymmetric Cell Division
• Induction
• Developmental Genomics
• Cell Competence
• Genetic Redundancy
• Positional Information
• Differential Determination
• Lateral Inhibition
• Genetic Networks

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Asymmetric Cell Division

• Asymmetric cell divisions are cell division in
  which the daughter cells obtain different fates
  from one another, either by segregation of some
  cytoplasmic determinants or through signaling
• Symmetry breaking process via differential
  offspring following mitosis
• Eg. Volvox
• Somatic cell
• Gonadidia cell

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Cellular Induction

• Induction is a process in which a cell or tissue
  signals to another cell or tissue to effect its
  developmental fate
• Symmetry Breaking process

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Developmental Genomics

• Developmental genomics is the creation and use of
  tools and techniques to study differences in the
  genomes and the biological functions of
  individual genes among related organisms (e.g.,
  QTL, SNP)

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Cell Competence

• Competence is the ability of a cell or tissue to
  respond to an external signal, often from an
  adjacent cell or tissue

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Genetic Redundancy

• Genetic redundancy means that two or more genes
  are performing the same function and that
  inactivation of one of those genes has little or
  no effect on phenotypes.

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Positional Information

• Positional information refers to an underlying
  informational field that cells sense and
  interpret according to their genetic background
  and developmental history, which provides the
  basis for pattern formation
• The role of Ubx (Hox gene Ultrabithorax)

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Cell Determination

• Determination is a classical term used to define
  the capacity of a cell to acquire different fates
• Heterochrony in totipotency via differential
  timing in mitosis

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Lateral Inhibition

• Lateral signaling is a process in which
  neighboring cells inhibit each other from
  developing in a similar way

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Degrees of Freedom in the Genome

• Transcription from DNA to mRNA
• mRNA splicing
• Nuclear to cytoplasmic transport rates
• mRNA stability
• mRNA transcription
• Protein enactment

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The fruit of the human genome project
This is More Complicated Than We Thought!?