Chapter 14 - Development

Question 1

Process of differentiation

Answer 1

Self-organizing chemical reactions concentrate certain chemicals at each end of “seed” cell, hence each daughter cell has slightly different chemical composition
Genes switched on and off by special molecule, so different set of genes active in each cell
Without genetic blueprint (see theory of differentiation), coordinated in stages, cell only has to choose between 2 or 3 paths at a time - cells channed through self-organized bifurcation towards increasingly specific types as more and more genes are switched off. Eventually each cell in mature organism produces specific protein for one type of cell
Only few of possible combos of genes will produce viable cells
Network of genes doesn’t have to go through process of searching but attracted rapidly towards stable patterns

Question 2

Theory of differentiation (falliable)

Answer 2

Controlled by small group of “master” genes
- same in every cell, hence they’re in no better pos than other genes to know which proteins are needed at particular loc and stage of dev
- Computer software suggests that hierarchical control system wouldn’t be stable enough to produce reliable dev, esp when genes are continuously deleted, moved, duplicated, and changed
- Response of dev organisms to injuries indicate that parts communicate with each other, changing type of cell they become as necessary to repair damage; such a process can’t be centrally controlled

Question 3

Process of morphogenesis

Answer 3

How cell types are assembled and organized, idea of genetic blueprint is inadequate
Single gene may affect several traits, and particular trait may be produced by interaction of many
Effect of gene may be modified or reversed by environment
Development is holistic process, depends on interaction of genes and environment
Genes more like recipe than blueprint

Question 4

Physical form

Answer 4

molecular composition itself isn’t sufficient to explain, requires self-organization and morphogenetic fields
Dev and regeneration suggest cells “know” where they are in relation to whole organism
If cells can distinguish chemical concentration they can determine where they are
Patterns created by positive and negative feedback loops of chemical reactions could guide formation of organism and sequence of stages through which it develops

Question 5

Self-organized pattern

Answer 5

Takes little information, requires few genes, like fractals

Question 6

Morphogenetic fields

Answer 6

Form not determined by genes
Form not selected to improve organisms’ prospect for survival
Forms energe from interaction of cell chemistry and structure with changing shape of organism and characteristics of environment - holistic process

Question 7

Archetypes and wholeness

Answer 7

Development of every organism guided by resonance with morphic fields associated with similar organisms - a self organized and evolving archetype