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Chapter 3

Psyc100-Ch3 - Genes Environment Behavior.docx

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PSYC 100
Jaime Palmer- Hague

Psychology 100 Chapter 3: Genes, Environment, Behaviour G ENETIC I NFLUENCES ON B EHAVIOUR Genotype: the specific genetic makeup of the individual Phenotype: the individual’s observable characteristics  Some genes’ directives are used on one occasion, some on another. Some are never used at all, either because they are contradicted by other genetic directives or because the env never calls them forth. Eg) chicken have genetic code for teeth, but they don’t have teeth. Genetic Makeup (p.63): The human body Each human cell Each nucleus containsOne chromosome of Each chromosome (except red blood contains numerous contains 100 trillion cells) contains a 46 chromosomes, every pair is from genes, segments of cells arranged in 23 pairs. each parent. nucleus. DNA. Chromosome: a double-stranded and tightly coiled molecule of DNA  egg cell and sperm cell carry chromosomes within their nuclei the material of heredity  DNA carries genes: biological units of heredity (segments of DNA) Alleles: alternative forms of a gene that produce different characteristics  Eye color genes have different allele (produce blue eyes, brown eyes, etc)  Genotype (genetic structure) and Phenotype(outward appearance) are no identical, because some genes are dominant while some are recessive.  if both genes from parents are dominant, the particular characteristics that it controls will be displayed  if one gene received from parent recessive, the characteristics will not show up unless the partner gene inherited from the other parent is also recessive D+R=D ; R+R=R  eg) a child will only have blue eyes if both parents have blue eyes. If one inherits a dominant brown eye gene and a recessive gene for blue eyes, he will have brown eye and the blue-eyed trait will remain hidden in his genotype. Eventually this recessive gene will be passed to his own offspring  Polygenic transmission: a number of gene pairs combine their influences to create a single phenotypic trait BEHAVIOR GENETICS (p.65)  study how influence of genetic and environmental factors influence psychological characteristics/individual differences in behavior  Family relatedness: Probability of sharing any particular gene with identical twins is 1.00. With parents or siblings is 50%. With grandparent or half siblings it’s 25%. STUDYING GENETIC SIMILARITIES 1. Family studies: study family members to see if genetic similarities is related to similarity on a particular trait  if more closely related people are more similar on the trait in question, this points to a possible genetic contribution 2. Adoption studies: people who were adopted early in life are compared on some characteristics with both their biological parents and adoptive parents  if adopted person are more similar to biological parents, a genetic influence on that trait is indicated  if more similar to adoptive parents, environmental factors are judged to be more important for that trait 3. Twins studies: compare trait similarities in identical (monozygotic) and fraternal (dizygotic) twins  Measure concordance rates (trait similarity) HERITABILITY: genetic influences (p.66) Heritability statistic: estimates the extent to which the difference in a specific phenotypic characteristic within a group of people can be attributed to their differing genes Max value = 1.00 (100% of the variance) Rules: 1. Applies only to a particular group in a particular Environment (higher heritability within similar environment –eg higher IQ from richer families) 2. Estimates do not apply to individuals, only to variance within a group 3. Even highly heritable traits can be modified by an environment Genotype Shared Environment Unshared Environment ↘ ↓ ↙ Group variation on a psychological trait  Shared environment (home, classroom): people who reside in them experience many of the same features  Unshared environment (social gathering): even siblings have own unique experiences with parents or friends  These environments and genotype contribute to group variance on particular characteristics  Intelligence has a strong basis with heritability in the 50%-70% range. See chart on p.71. shared environment&educational experiences are important.  Personality has a weaker genetic contribution, shared env has no impact but unshared experiences has more significance on development of personality traits G ENE -E NVIRONMENT INTERACTIONS How the Environment influence Gene (p.73) Reaction range: for a genetically i
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