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Nature vs. Nurture-3
What makes us human?
Nurturist position: Beyond Human Nature by Jesse J. Prinz -- Norton
Fall 2016
D.D. Reeder
1
Extremes
Nature: total Genetic determinism
(deterministic)
Nurture: “Blank Slate” (nothing genetic)
(only physical phenotypes are heritable)
Truth is in between
– but this obvious answer is insufficient.
Mendel -- “laws” of inheritibilty
Driesch – established cell differentiation
genetics
epigenetics
Trait appearing “innate” or “instinctive” is NOT determined
solely from our genes (may still not be learned)
Fall 2016
D.D. Reeder
2
A Look Ahead
Inheritance (transmission to the next generation)
gamete
experience
Genome
Socially modified behavior (education)
Epigenome ?
Mothers diet (Cellular environment)
Fall 2016
D.D. Reeder
3
Twins
To attempt to test:
fix environmental experience -- then variation must be due to innate traits
BUT – life experiences cannot be identical for two humans
~1885 Hans Driesch published his studies on embryology
- experimenting on sea urchins.
at first division after conception -- cells were separated
Complete organisms – not halves
innate fixed and variance must be due to environment
Fall 2016
D.D. Reeder
4
Twin phenotypes
Despite identical DNA
Different fingerprints
Color blindness (Dionne quints)
Eye color ?
Right handed
~90%
Left handed
~10%
Infant handedness correlated with in utero handedness
Cloning 1996 -- Dolly
phenotypes observed
Even physical phenotypes are genetically non-determinate
-- but not learned!
Fall 2016
D.D. Reeder
5
Suicides
NO human experiments
Which cells might be important?
Neurons!?
Search for epigenetic marking in DNA from the brain
Suicides suffering child abuse
Suicides not suffering child abuse
Accidental deaths
Fall 2016
D.D. Reeder
6
DNA
DNA is a linear chain of
base pairs (4) linked to
an inert backbone
Chromosomes are packaged
DNA All 23 in nuclei of all cells
(except hemoglobin)
Histones
Information is contained in
punctuated sequences of
these base pairs
A Gene is the sub-sequence
needed to build a protein
(combination of amino acids)
Fall 2016
D.D. Reeder
7
Repair
Errors/damage frequent
External damage or during mytosis
Need correction/repair
Despite complexity and the considerable energy required
all multicelled creatures have such a repair mechanism
Not 100% effective
All multicelled organisms have DNA repair
(as well as cell replacement or repair)
Significant energy is allotted to repair
Just one double-strand break could require >10,000 ATP molecules
Spring 16
PLATO
8
Mutation
DNA is template
Replication
Damage
Point defects
Single strand breaks
Double strand breaks
Change in the sequence can be
passed to the next generation
sequential errors
abnormal chemical structure
Spontaneous (chance)
Induced (external to DNA)
>10,000 errors per cell per day (humans)
DANGER!
Germ cell
Somatic
Fall 2016
heritable
aging
cancer?
D.D. Reeder
9