Heredity

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Heredity Environment

• Chapter 3
• Jen Wright
• Psyc311
• Fall, 2008

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Chromosomes DNA
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Nature vs. nurture

• To what extent is development the product of our
  genetic endowment?
• To what extent is it the product of environmental
  influences?

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View 1

• Genes
• Environment

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• Scientist in many nations have studied thousands
  of twins, both monozygotic and dizygotic, raised
  together in the same home and raised separately
  in different homes

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• Notice identical twins are not identical.

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nature vs. nurture

• Which contributes more to childs development
• genes or environment?
• Which contributes more to the area of a rectangle
  
• length or width?
• The correct question to ask is which contributes
  more to variation within a given group (of
  children and rectangles)?

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• Trait A shows a high sibling correlation, but
  little heritability (i.e. high shared
  environmental variance low heritability).
• Trait B shows a high heritability since
  correlation of trait rises sharply with degree of
  genetic similarity.
• Trait C shows low heritability, but also low
  correlations generally this means Trait C has a
  high non-shared environmental variance.
• In other words, the degree to which individuals
  display Trait C has little to do with either
  genes or broadly predictable environmental
  factorsroughly, the outcome approaches random
  for an individual.

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View 2

• Genes
• Environment

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environments influence genes

• genotype
• An organisms entire genetic inheritance, or
  genetic potential
• phenotype
• The observable characteristic of a person,
  including appearance, personality, intelligence,
  and all other traits
• Lots of genes are carried in a persons genotype,
  but do not get expressed in their phenotype.
• "The phenotype is the unique consequence of a
  particular genotype developing in a particular
  environment"
• (Lewontin, 1982, pp. 2223).

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genes influence environment

• Each childs genes elicit other peoples
  responses, and these responses shape development.
  
• In other words, a childs environment is partly
  the result of his or her genes.
• Children, adolescents, and especially adults
  choose environments that are compatible with
  their genes (called niche-picking),
• thus genetic influences in adulthood increase.

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View 3

• Genes
• Environment

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• Phenotypic plasticity the degree to which an
  organism's phenotype is determined by its
  genotype.
• A high level of plasticity means that
  environmental factors have a strong influence on
  the particular phenotype that develops.
• Examples of high plasticity larval newts, social
  insects, plants.
• Where there is low plasticity, the phenotype of
  an organism can be reliably predicted from
  knowledge of the genotype, regardless of
  environmental peculiarities during development.
• Where there is high plasticity, phenotype cannot
  be reliably predicted from genotype.

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• Genetic canalization the extent to which an
  organism's phenotype allows conclusions about its
  genotype.
• A phenotype is said to be canalized if mutations
  (changes in the genome) do not noticeably affect
  the physical properties of the organism.
• a canalized phenotype may form from a large
  variety of different genotypes, in which case it
  is not possible to exactly predict the genotype
  from knowledge of the phenotype (i.e. the
  genotype-phenotype map is not invertible).

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ADHD

• Commonly boys who have male relatives with the
  same problem
• Overactive in all contexts, home as well as
  school
• Typically calmed by stimulants
• Ritalin, Adderall, and even coffee
• The rapid increase in ADHD
• from 1 to 5 of all U.S. children in the past 50
  years
• Many factors correlated with ADHD
• crowded homes, television, lead, food additives,
  rigid teaching

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addiction

• Inherited biochemistry makes people vulnerable to
  various additions
• Fewer dopamine receptors
• Environments contribute to the likelihood that an
  addiction will form

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nearsightedness

• Nearsightedness is a symptom in more than 150
  genetic syndromes
• Commonly inherited trait
• environment also influences nearsightedness
• diet is deficient of vitamin A
• large quantities of close-in vision (reading
  books/computer screens)

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IQ

• Fatty acids DHA and ARA promote neuronal
  growth/connectivity
• Breast milk is rich in DHA and ARA
• Absence of breast milk may negatively effect IQ
• Certain genes play crucial role in metabolism of
  these fatty acids
• if babies have these genes, they benefit from
  breast milk others dont.

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Others

• Political orientation (?!)
• Voting
• Liberal vs. conservative ideology
• Aggression
• Hormones