PSY Module 6

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What are chromosomes, DNA, genes, and the human genome? How do behavior geneticists explain our individual differences?
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Genes are the biochemical units of heredity that make up chromosomes, the threadlike coils of DNA. When genes are “turned on” (expressed), they provide the code for creating the proteins that form our body’s building blocks. Most human traits are influenced by many genes acting together. The human genome is the shared genetic profile that distinguishes humans from other species, consisting at an individual level of all the genetic material in an organism’s chromosomes. Behavior geneticists study the relative power and limits of genetic (our heredity) and environmental influences on behavior.
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environment
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every nongenetic influence, from prenatal nutrition to the people and things around us.
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behavior genetics
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the study of the relative power and limits of genetic and environmental influences on behavior
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heredity
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the genetic transfer of characteristics from parents to offspring
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chromosome
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threadlike structures made of DNA molecules that contain the genes
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DNA
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a complex molecule containing the genetic information that makes up the chromosomes
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genes
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the biochemical units of heredity that make up the chromosomes; segments of DNA capable of synthesizing proteins
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genome
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the complete instructions for making an organism, consisting of all the genetic material in that organism’s chromosomes
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Put the following cell structures in order from smallest to largest: nucleus, gene, chromosome
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gene, chromosome, nucleus
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When the mother’s egg and the father’s sperm unite, each contributes 23 ____________
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chromosomes
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How do twin and adoption studies help us understand the effects and interactions of nature and nurture?
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Studies of identical (monozygotic) twins versus fraternal (dizygotic) twins, separated twins, and biological versus adoptive relatives allow researchers to tease apart the influences of heredity and environment. Research studies on separated identical twins maintain the same genes while testing the effects of different home environments. Studies of adoptive families let researchers maintain the same home environment while studying the effects of genetic differences. Heritable individual differences (in traits such as height and weight) do not necessarily explain gender or ethnic group differences. Shared family environments have little effect on personality, though parenting does influence other factors (such as attitudes).
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identical (monozygotic) twins
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develop from a single fertilized egg that splits in two, creating two genetically identical organisms
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fraternal (dizygotic) twins
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develop from separate fertilized eggs. They are genetically no closer than ordinary brothers and sisters, but they share a prenatal environment
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How do researchers use twin and adoption studies to learn about psychological principles?
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Researchers use twin and adoption studies to understand how much variation among individuals is due to genetic makeup and how much to environmental factors. Some studies compare the traits and behaviors of identical twins (same genes) and fraternal twins (different genes, as in any two siblings). They also compare adopted children with their adoptive and biological parents. Some studies compare traits and behaviors of twins raised together or separately.
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How do heredity and environment work together?
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Our genetic predispositions and our specific environments interact. Environments can trigger or block genetic expression, and genetically influenced traits can evoke responses from others. The field of epigenetics studies the influences on gene expression that occur without changes in DNA.
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epigenetics
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the study of environmental influences on gene expression that occur without a DNA change. Study of environmental factors that affect how our genes are expressed.
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How do evolutionary psychologists use natural selection to explain behavior tendencies?
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Evolutionary psychologists seek to understand how our traits and behavior tendencies are shaped by natural selection, as genetic variations increasing the odds of reproducing and surviving in their particular environment are most likely to be passed on to future generations. Some variations arise from mutations (random errors in gene replication), others from new gene combinations at conception. Humans share a genetic legacy and are predisposed to behave in ways that promoted our ancestors’ surviving and reproducing. Charles Darwin’s theory of evolution is an organizing principle in biology. He anticipated today’s application of evolutionary principles in psychology.
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evolutionary psychology
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the study of the evolution of behavior and the mind, using principles of natural selection
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natural selection
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the principle that those chance inherited traits that better enable an organism to survive and reproduce in a particular environment will most likely be passed on to succeeding generations
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mutation
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a random error in gene replication that leads to a change
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How are Belyaev and Trut’s breeding practices similar to, and how do they differ from, the way natural selection normally occurs?
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Over multiple generations, Belyaev and Trut selected and bred foxes that exhibited a trait they desired: tameness. This process is similar to naturally occurring selection, but it differs in that natural selection is much slower, and normally favors traits (including those arising from mutations) that contribute to reproduction and survival.
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interaction
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the interplay that occurs when the effect of one factor (such as environment) depends on another factor (such as heredity).
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A small segment of DNA that codes for particular proteins is referred to as a
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gene
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Fraternal twins result when
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two eggs are fertilized by two sperm.
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Epigenetics is the study of the molecular mechanisms by which _________ trigger or block genetic expression.
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environments
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Behavior geneticists are most interested in exploring ____________ (commonalities/differences) in our behaviors. Evolutionary psychologists are most interested in exploring ____________ (commonalities/differences).
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differences, commonalities
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Evolutionary psychologists are most likely to focus on
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natural selection of the fittest adaptations.
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Environmental events “turn on” genes, rather like hot water enabling a tea bag to express its flavor. When turned on, genes provide the code for creating:
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protein molecules
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_____ are a major source of genetic diversity.
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mutations
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Our experiences create _____, which are often organic methyl molecules attached to part of a DNA strand.
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epigenetic marks
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_____ is the principle that, among the range of all inherited trait variations, those that lead to increased reproduction and survival will most likely be passed on to succeeding generations.
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natural selection
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Luther was born with one kidney. This variation in an inherited trait is most likely caused by:
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a mutation
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Which traits will be MOST alike in two biologically unrelated adopted children raised by the same adoptive parents?
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values
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Dr. Chu studies the environmental influences on gene expression by studying identical twins that have been reared apart. Dr. Chu field of study is called:
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epigenetics
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Approximately what percent of genes are shared by all human beings?
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99.9%
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Sam’s sister has an independent study proposal due next week, and she has asked for help deciding on a topic. She is interested in studying what makes humans so similar to each other. He should recommend that she focus on _____.
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evolutionary psychology

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