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Chapter 4

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Psychology 1000
Terry Biggs

Michael Hua Psychology 1000 Chapter 4: Genes, Evolution, and Behavior October 2, 4, 9, 11/2012 Prof: Dr. T Biggs Genes > the functional units of heredity; they are composed of DNA and specify the structure of proteins Chromosomes > rod-shaped structures within every body cell that carry the genes DNA > the chromosomal molecule that transfers genetic characteristics by way of coded instructions for the structure of proteins Genome > The full set of genes in each cell of an organism Chromosome & Genes  Genotype – Specific genetic makeup – Present from conception – Never change – fixed from the moment of conception  Phenotype - Observable characteristics - Can be altered by other genes, environment  E.g., how tall you can grow vs. how tall you “actually” grow  Chromosome - Molecule of DNA - Contains many genes  Genes - Contain genetic blueprint  Every cell has 46 chromosomes (23 pairs)  Exception: Egg & Sperm - Contain 23 chromosomes - Combine to form new cell with 46 chromosomes  Heredity encoded in combination of bases, adenine, thymine, guanine, and cytosine  Genes contain bases, carry codes for protein manufacture Dominant, Recessive & Polygenic  Dominant Gene: if a person receives a dominant gene from either parent, they will display the characteristic the gene controls  Recessive Genes: if the gene is recessive, the characteristic WILL NOT be displayed unless its partner gene inherited from the other parent is also recessive (require one from each parent)  Polygenic Transmission (multiple gene pairs influence phenotype)  i.e. refer to a Punnett Square Mapping the Genetic Code Michael Hua  Human Genome Project (1990) - More than 75 genes that contribute to hereditary diseases have been identified Genetic Engineering  Recombinant DNA procedures - Enzymes cut DNA - Combined with DNA from another organism - Inserted into host cell  Gene Knockout - Particular function of gene is eliminated  Problem - Few behaviors are controlled by single gene Behavioural Genetics  Study of genetic relatedness - With parents = 50% - Siblings = 50% - Grandparents = 25%  Heritability coefficient - Estimate of how much of characteristic is due to genetic factors  Concordance Rate - Rate of co-occurrence of a characteristic among individuals - Higher rates among individuals who are more highly related to one another = possible genetic contribution  How Study? - Adoption studies; twin studies Monozygotic & Dizygotic Twins Michael Hua  Monozygotic Twins - Identical chromosomes  Dizygotic Twins - Different chromosomes Adoption & Twin Studies  Adopted children – frequently more similar to biological parents  Identical twins more similar – even when reared apart Twin Studies compare: Adoption Studies: Twins - Monozygotic (MZ) separated at birth Twins are genetically identical - Compare twin with both adoptive and biological parent - Dizygotic (DZ) Twins share 50% of genetic - Helps determine heritability of endowment twins Genetic Influences on Behavior  Intelligence - Is it genetics or environment?  If it is completely controlled by genes - Individuals with same genes should have same IQ scores - Identical Twins – Correlation = .86 - Parent-child – correlation = .36  More important question - How do genes and environment interact? Reaction Range  Are there genetically determined „boundaries‟ on the expression of a trait?  Reaction range - Range of possibilities – upper and lower limits – that the genetic code allows - Individual inherits a range for potential expression of a trait - Environment effects determine where person falls within these limits Behavior Genetics and Personality  Is there a genetic component to our personality?  Need to study - Genetic contribution - Shared family environment - Unique Individual experiences  How study? Need 4 groups - Identical twins reared-together & apart - Fraternal twins reared together & apart Minnesota Twin Study  Genetic factors accounted for 39-58% of variation Michael Hua  Unique experiences accounted for 36-56% of variation  Familial environment accounted for little or no variation Other Research  Attitudes have an inherited component - Attitudes toward preservation of life, equality, athleticism – highest genetic component - Certain inherited characteristics may predispose people to certain activities  Others include: - Tendency to abuse alcohol, personality disorder dimensions, seasonal mood changes Comparison Genetic Enviro Conclusion Used to Estimate Sim Sim Genetic Influences: The Whole Picture Michael Hua Genetic Influences: Misconceptions Misconception Correct Understanding Genetic Counselling  What do Genetic Counselors do? Michael Hua  Provision of medical information about genetic disorders & risks  Help individuals make decisions about their health, pregnancies, or their child‟s health care Evolution & Behaviour  Evolutionary Psychology - How behavior & tendencies have evo
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