Week 2 Ch 2

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Department
Cognitive Sciences
Course
PSYCH 9A
Professor
Thomas Michael D' Zmura
Semester
Winter

Description
Chapter 2: The Genetic and Evolutionary Roots of Behavior Genetics and DNA • Chromosomes- structures in the nucleus of each cell that contain the genes, the units of hereditary transmission; human cell has 46 chromosomes arranged in 23 pairs • DNA- the complex molecule that is the constituent of genes Genes • DNA molecule forms double helix; subunits are adenine, thymine, cytosine, guanine • Base pairs allow DNA to carry instructions for proteins • Gene- a section of a DNA molecule that contains instructions for how and when to assemble a protein. Genes are located on chromosomes. Gene Expression • Environment outside the cell can affect whether a gene will be expressed • Timing: some genes active early in organism’s development but not later • Organism’s overall environment and its behavior  temperature, stimulation, interactions • Genotype- complete set of an organism’s genes  defined by the specific sequence of genes on each of its chromosomes • Phenotype- overt characteristics and behaviors of an organism  defined by what the organism is actually like o Product of both genotype and the environment Gene Transmission • Matter of chance which of the father’s/mother’s chromosomes go into each egg Interactions among Genes • Gregor Mendel and pea plants • Allele- an alternative form of a specific gene • Dimples are dominant- term for a gene that directs the development of a certain characteristic even when the corresponding gene on the other chromosome is different – i.e., some other allele o Recessive- a term for a gene that directs the development of a particular characteristic only if the corresponding gene on the other chromosome matches it – i.e., is the same allele • Genotype may not always lead to phenotype o Ex. PKU depends on diet, not just recessive alleles of that particular gene o Codominance- both genes in the pair affect the phenotype  Ex. Blood type o Incomplete dominance- person with two different alleles with have a phenotype that’s intermediate between the types favored by each allele on its own  Ex. Serotonin transporter gene Polygenic Inheritance • Polygenic inheritance- a pattern in which many genes all influence a single trait Evolution By Natural Selection • Proximate causes- the influences within an organism’s lifetime that led to its particular traits or behaviors • Ultimate cause- the reasons why, over many years of evolution, a particular trait or behavior helped members of a population to survive and reproduce The Principles of Natural Selection • Natural selection- the mechanism that drives biological evolution; it refers to the greater likelihood of successful reproduction for organisms whose attributes are advantageous in a given environment • Naturalistic fallacy- the (mistaken) idea that anything “natural” must be “good” Genes and Evolution • Darwin’s 3 important principles: o 1. Must be variation among individuals within a population o 2. Certain of the variants must survive and reproduce at higher rates than others o 3. Traits associated with this superior survival and reproduction must be passed from parents to offspring • How variety occurs o Mutations- errors in the replication of DNA Evidence for Evolution by Natural Selection • Three spine stickleback • Vestigial structures The Unity of Life • All of Earth’s living things are derived from a common lineage • Jellyfish with green fluorescent protein  inserted into monkeys, makes monkeys green The Genetics and Evolution of Behavior • Psychological traits are a part of an animal’s phenotype o If the phenotype will make the animal more likely to survive/reproduce, the animal’s genes will be well represented in the next generation • Evolution has favored mechanisms that produce flexibility in how an animal acts o Need for flexibility is amplified by the process of niche construction- the process in which organisms, through their own behaviors, alter the environment and create their own circumstances The Biological Roots of Smiling • Sometimes, style of communications is species specific- pertaining to just one species • The Origins of Smiling o The behavior of smiling is species general- pertaining to all organisms in a species o Smiling was the most accurate identification in an experiment with Americans and New Guinea tribesmen in describing each other’s emotions • Smiles in Other Species o Darwin’s The Expression of the Emotions in Man and Animals o Expressive smile  produced even if no one around, change in mouth’s shape, formation of crow’s feet- lines that radiate outward from the eyes o Pol
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