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Chapter 4

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Psychology 1000
Terry Biggs

Chapter 4 Notes Genes. Evolution, and Behavior - Genes – The functional units of heredity, they are composed of DNA and specify the structure of the 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 ach cell of an organism - Genotype o Specific genetic makeup o Present from conception o Never change - Phenotype o Observable characteristics produced by the genetic endowment o Can be altered by other genes or the environment (usually due to ingestion ex. Eating asparagus) o Ex. People who are genetically supposed to become tall but live in an environment that stunts their growth (such as getting rickets) and so they never grow to the height they should have (the phenotype affecting the genotype) - A chromosome is a tightly coiled molecule of DNA that contains many genes - Genes contain the genetic blueprint for you - Every cell has 46 chromosomes (23 pairs) and every cell nucleus in your body contains the genetic code for your entire body - Exception: egg and sperm o Contain 23 chromosomes o Combine to form new cell with 46 chromosomes - Heredity encoded in combinations of bases adenine, thymine, guanine, cytosine - Genes contain bases, and carry codes for protein manufacture - Alleles are alternative forms of a gene that produce different characteristics - 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 - Polygenic transmission (multiple gene pairs influence phenotype) - The Human Genome Project (1990-2001) mapped out the entire human genetic code - Humans have about 25,000 genes - Genetic Engineering o Recombinant DNA procedures  Enzymes cut DNA  Combined with DNA from another organism  Inserted into host cell o Gene knockout  Particular function of a gene is eliminated, and then behavior is observed o Problem  Few behaviors are controlled by a single gene it is usually because of the interaction of many genes - Behavioral Genetics o Study of genetic relatedness  With parents = 50%  Siblings = 50%  Grandparents = 25%  This increases variety among us  Breeding with those who you are related to is anti-survival because it tends to usually surface all the bad characteristics/genes o Behavior geneticists are interested in studying how hereditary and environmental factors combine to influence psychological characteristics o Heritability coefficient  Estimate of how much of a characteristic is due to genetic factors  But even in identical twins, they may not be exactly the same because they have different experiences (the environment changes them) o Concordance Rate – Co-occurrences; a higher concordance in people who are more highly related to one another, then this points to a higher genetic contribution (especially if they are in different environments). This Is studied with adoption studies and twin studies o Adoption Study – a person who was adopted early in life is compared on some characteristic wit the biological parents and the adoptive parents. If the person is more similar to the biological parents a genetic influence is suggested, but if they are more similar to the adoptive parents than environmental factors were probably more important. Identical twins tend to show more relation to their biological parents o Twin studies – If identical twins are more similar than fraternal twins, a genetic factor is more involved.  Monozygotic twins – identical chromosomes  Dizygotic twins – Different chromosomes  Even if they are reared in different environments twins are likely to be very similar due to genetics  Studies have demonstrated that sometimes environmental factors interact with genetic endowment in important ways - There is a predisposition set by your genes - Genetic Influences on Behavior o Our characteristics arise from the combination of our learning experiences and the environment in which we behave acting on a substrate provided by our genetic makeup o Heredity, environment and intelligence – it has been proven that about 50-70 % of the variation in IQ is accounted for by genetic factors. If intelligence was controlled by genes that individuals with the same genes should have the same IQ (but the correlation is only .86) o Biological Reaction Range, the environment, personality and intelligence  The reaction range is the range of possibilities (upper and lower limits) that the genetic code allows for a trait  There is a given range set by genetic endowment and then the actual characteristic is determined by the effect of the environment o Behavior Genetics and Personality  Personality theorists work towards tracing differences in personality characteristics to specific differences in the brain  There is genetic contribution, a shared family environment, and unique individual experiences the contribute to personality  Big Five  Extraversion-Introversion (outgoing vs. quiet)  Agreeableness (helpful, cooperative vs. antagonistic)  Conscientiousness (responsible vs. undependable)  Neuroticism (worrying vs. calm)  Openness to experience (imaginative vs. lacking curiosity)  Genetic factors account for a significant amount of these personality differences  This is also studied using twins (both identical and fraternal reared together and apart)  Minnesota Twin Study – Genetic factors can account for 39- 58% of variation, unique experiences accounted for 36-56% of variation which familial environment accounted for little to no variation  Attitudes have an inherited component – Attitudes toward preservation of life, equality, and athleticism have the highest genetic component. Certain inherited characteristics may predispose people to certain activities (other characteristics include alcohol abuse, personality disorder dimensions, and season mood changes) Comparison Genetic Similarity Environmental Similarity Conclusion Used to Estimate - Genetic Counselors – Genetic counselors provide medical information about genetic disorders and risks. This helps individuals make decisions about their health, pregnancies, or their child’s health care - Evolution and Behavior o Evolutionary Psychology studies how behavior and tendencies have evolved in response to environmental demands o Biologically based mechanisms receive input from the environment, process it, and the respond. Without this there could be no behavior o Behavior doesn’t evolve, genetically produced physical structures that interact with the demands of the environment produce a behavior o Evolution of Adaptive Mechanisms  Evolution is a change over time in the frequency with which particular genes, and the traits they produce, occur within an interbreeding population  Some genetic variations arise from mutations, random events, and accidents in gene reproduction during the division of cells  Natural selection – the principle that states that characteristics that increase the likelihood of survival and ability to reproduce within an environment will most likely be preserved in the population and will become more common over time  Adaptations are the products of natural selection. They allow organisms to meet recurring environmental challenges to their survival, thereby increasing their reproductive ability (eg. Tarahumara people)  Successful human behavior
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