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Chapter 4

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Anthropology 1026F/G

Psychology Chapter 4 Notes Genetic Influences Our genetic endowment combines with environmental forces to determine our behavior Chromosomes And Genes Hippocrates suggested that semen contains not body parts, but rather some sort of design for the formation of offspring Gregor Mendal, a monk whose research with garden peas in the 1860s marked the beginning of modern genetic theory Mendal showed that heredity involves the passing on of specific organic factors, not a simple blending of the parents characteristics. The offspring of one set of parents do not all inherit the same traits as is evident in the differences we see among brothers and sisters Genotype= the specific genetic makeup of an individual Phenotype= the observable characteristics produced by that genetic endowment. Some are used at one occasion; others are never used at all, either because they are contradicted by other genetic directives or because the environment never calls them forth. Thus genotypes are present from conception and never change, but phenotype s can be affected by other genes and by the environment. Chromosome=A tightly coiled molecule of DNA that is partly covered by protein The DNA portion of the chromosome carries the hereditary blueprint in unites called genes. In humans, every cell has 46 chromosomes The sex cell which is the only exception has 23 The 23 from the egg combines with the 23 of the sperm creating a zygote Zygote= contains 46 chromosomes The genes within each chromosome also occurs in pairs so that the offspring receives one of each gene pair from each parent. Every cell nucleus in your body contains the genetic code for your entire body. In all these cells (except for egg and sperm), there are 2 copies of each gene, one from your mother and one from your father. Alternative forms of a gene that produce different characteristics are called Allels Genes affect our bodys development and functioning through our general mechanism: genes code for the production of proteins. Approximately 70,000 different types of proteins are found in a human control the structure of individual cells and all the chemical reactions that go on within those cells, whether they are reaction necessary to sustain the life of the cell, or are changes induced periodically by experience or maturation. It is estimated that about half of all genes target brain structure and function. Each individual gene carries the code for a specific protein, and when that gene is activated, the cell produces the specified protein. At different points in development, in response to different environmental factors a gene may be activated and a protein produced or an already active gene may be turned off and the levels of a specific protein will then decrease. As the protein levels within a neuron change, there is a corresponding change in the function of that neuron and the neural circuits in which it participates. Dominant, Recessive, and Polygenic Effects If a gene in the pair received from the mother and father is dominant, the particular characteristic that it controls will be displayed; is the gene is recessive, the characteristic will not show up unless the partner gene inherited from the other parent is also recessive In greater many instances, a number of genes pairs combine their influences to create a single phenotypic trait. This action is also known as polygenic transmission, and it complicates the straightforward picture that would occur if all characteristics were determined by one pair of genes. The discovered humans have fewer genes than expected; a human has approximately 25,000 genes and not the 100,000 originally estimated. Genetic Engineering: The Edge Of Creation To duplicate and modify the structure of genes themselves. In recombinant DNA procedures, researchers use certain enzymes to cut the long threadlike molecules of genetic DNA into pieces, combine them with DNA from another organism, and insert them into a host organism, such as a bacterium. Inside the host, the new DNA combination continues to divide and produce many copies of it self. Scientists have used this procedure to produce human growth hormones Molecular biologists have developed methods for inserting new genetic material into viruses that can infiltrate neurons and modify their genetic structure. Altering a specific gene in a way that prevents it from carrying out its normal function= Gene Knockout, because that particular function of the gene is eliminated. The effects on behavior are then observed Loss of the serotonin reuptake mechanism results in serotonin remaining in the synapse after its release and a consequent alteration in the activity of serotonin releasing neurons and serotonin receptors. Very few behaviors are controlled by a single gene If a behavior does occur, it doesnt mean that that single gene was responsible. It may disrupt a wide range of functions Genetic engineering gives humans potential control over the processes of heredity and evolution In Review Heredity potential is carried within the DNA portion of the 23 pairs of chromosomes in units called genes. Genotype and phenotype are not identical because some genes are dominant while others are recessive. Many characteristics are polygenic origin that is influenced by interactions of multiple genes. Genes influence the development, structure and function of our body, including our brain by controlling the production of proteins Genetic engineering allows scientists to duplicate and alter genetic material or, potentially, to repair dysfunctional genes.Behavior Genetics Techniques Knowledge of the principles of genetics transmission tells us how genetically similar people are depending on their degree of relatedness to one another Children get half of their genetic material from each parent. From grandparents we get a chance of 0.25% to inherit their genes. Behavior genetics are interested in studying how hereditary and environmental factors combine to influence psychological characteristics The extent to which variation in a particular characteristic within a group can be attribute to genetic factors is estimated statistically by a heritability coefficient Heredity= the passage of characteristics from parents to offsprings by way of genes; heredibility means how much of the variation in a characteristic within a population can be attributed to genetic differences It is important to note that heredibility refers to differences or variance, in the trait across individuals and not to the trait itself. Hereditability applies only to differences within a group not to differences between groups. Important to know what group was studied The hereditability coefficient is a statistical estimate of how much of the variability within a group is due to genetic factors. If the environment does not account for the variation in intelligence within this group, then the difference could be due to genetic factors and the heredibility coefficient would estimate a high value If a characteristic has higher concordance, or co-occurrence, in people who are more highly related to one another then this points to a possible genetic contribution, particularly if the people have lived in different environments. One research method based on this principle is the adoption study, in which a person who was adopted in early life is compared to some characteristics both with biological parents with whom the person shares genetic endowment, and with the adoptive parents, with whom no gene are shared. Seymour Kety and coworkers (1978) identified formerly adopted children who were diagnosed with the disorder later in life The researchers found that 12% of biological family members also had been diagnosed with schizophrenia, compared with a concordance rate of only 3% of adoptive family members suggested a hereditary link Twin Studies= are one of the more powerful techniques used in behavior genetics. Monozygotic (identical twins) develop from the same fertilized egg, so they are genetically identical. Dizygote= (fraternal) twins develop from two fertilized eggs so they share 50% of their genetic endowment Sometimes they are able to find and compare sets of identical and fraternal twins who were separated very early in life, and raised in different environments Both adoption and twin studies have led behavioral genetics to conclude that may psychological characteristics, including intelligence, personality traits and certain psychological disorders have a notable genetic contribution. Behavior genetics studies have demonstrated that environmental factors interact with
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