PSYCO104 Lecture Notes - Lecture 4: Determinism, Guanine, Twin Study

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12 Nov 2015
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Topic 4: Genes, Evolution, and Behavior
Genetic Influences
Chromosomes and Genes
- Chromosome
oMolecule of DNA
oContains many genes
- Genes
oContain genetic blueprint
- Every cell has 46 chromosomes (23 pairs)
oException: eggs and sperm, red blood cells
o23 chromosomes
oform new cell with 46 chromosomes
- Heredity encoded in combinations of bases adenine, thymine, guanine, and
cytosine (A, T, C, G)
- Genes contain bases, carry codes for protein manufacture
- How do genes influence our development and function?
oThrough coding for the production of proteins
- Protein production can be increased or decreased by a gene being activated or
deactivated
oAs protein levels within neurons change, there is a corresponding change
in the function of the neuron and the neural circuits in which it participates
Dominant, Recessive, and Polygenic
- Some genes are dominant, some recessive
- If a gene in a pair is dominant, the characteristic it controls will be displayed
- If a gene in a pair is recessive, the characteristic will not show up unless the
partner gene is also recessive
- When a number of gene pairs combine to crease a single phenotypic trait, it is
known as polygenic transmission
Genetic Engineering
-Recombinant DNA Procedures:
oEnzymes cue DNA
oCombined with DNA of another organism
oInserted into host cell
-Gene Knockout:
oParticular function of gene eliminated
oProblem: very little behavior is controlled by a single gene
Also, multiple systems can be affected by a single gene
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Behavior Genetics
-Behavior genetics is the study of how genetic and environmental components
lead to changes in behavior
-Heredity: passage of characteristics from parents to offspring by way of genes
-Heritability: how much of the variation in a characteristic within a population can
be attributed to genetic differences
-Heritability Coefficient: Estimate of how much of a characteristic is due to
genetic factors
-Concordance Rate:
oRate of co-occurrence of a characteristic among individuals
oHigher rates among individuals who are more highly related to one
another = possible genetic contribution
- Studied using adoption and twin studies
Genetic Influences on Behavior
Heredity, Environment, & Intelligence
Reaction Range
- Are there genetically determined “boundaries” on the expression of a trait
-Reaction Range:
oRange of possibilities that genetic code allows
oInherit range for potential expression
oEnvironmental effects determine where person falls within these limits
oReaction range may cover 15-20 IQ points
Behavior, Genetics, & Personality
- Is there a genetic component to our personality?
- Need to study:
oGenetic contribution
oShared family environment
oUnique individual experiences
- How to study? Need 4 groups
oIdentical twins reared together and apart
oFraternal twins reared together and apart
- Minnesota Twin Study
If it is completely controlled by
genes
Individuals with same genes
should have same IQ scores
Accounts for 50-70%
More important
question
How do genes and
environment
interact?
Intelligence
Genetics or
environment?
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