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Chapter 3

Chapter 3

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University of Toronto St. George
Michael Inzlicht

Genetic and Biological Foundations What is the Genetic Basis of Psychological Science? - Major event in the biological revolution was the Human Genome Project o Mapped the entire structure of human genetic material - Within nearly every cell, there is a genome o Genome provides instructions for everything, from how to grow a nose to where to place it on the body What part of the body the cell becomes is determined by which genes are turned on and off within the cell and this is determined from the cues from outside the cell Genome option, environment determines which option is taken Turning on and off of genes provides insight how physical bodies develop and how the brain works Genetics typically used to describe how characteristics are passed down by inheritance, but also refers to the process of turning on and off of genes - Within each cell there are chromosomes, which are structured made up of genes o Typical human: 23 pairs, half of each from different parent Genes are components of DNA Gene unit of heredity that determines a particular characteristic in an organism Segment of DNA that is involved in producing proteins that carry out specific tasks o Gene expression process by which genes produce the RNA and the proteins they then produce or switching a gene on Gene: how to produce proteins, when to produce proteins, environment determines this The environment during development is likely to cause genes to switch on or off www.notesolution.com Genes option, environment determined which action is taken Gene expression plays a role in specializing cells for specific functions Gene expression physical body Gene expression involved in al psychological activity allows us to learn, see, fall in love DNA is a double helix of sugar, phosphate and nitrogen molecules The sequence of molecules along the DNA strand specifies and exact instruction, through the production of RNA, to manufacture distinct proteins o Proteins: Thousands different types Basic chemicals that make up the structure of the cell and direct it activities - The relatively small number of gens in the human DNA (30 000) suggests that the complexity of humans is not simply due to our processing a large number of gens, but more likely due to subtleties in the way that genes are expressed and regulated - Important to understand how genes interact o How to alter gene function 1. Heredity involves passing along genes through reproduction - Selective breeding was used by Mendel to discover that there a mechanisms responsible for heredity - From his experiment Mendel deduced that there are units of heredity (now referred to as genes) that exist in two versions o Alleles are the versions of genes Dominant alleles (genes) are expressed whenever they are present Recessive alleles (genes) are expressed only when they are matched with similar gene (another recessive gene) a. Genotype and phenotype www.notesolution.com - The existence of dominant and recessive gens means that not all genes are outwardly expressed - Genotype the genetic constitution determined at the moment of conception, the actual genetic make up - Phenotype observable physical characteristics that result from both genetic and environmental influences o Example: for Mendel, even thought he had two purple flowers and the had the same phenotype, they could have had different genotypes (one being PP and the other being Pp) - Environmental factors that could affect the phenotype: good nutrition bigger size, sun tan change in complexion b. Polygenic effect - When there is a certain variability for a trait (such as height) within a population indicates that the characteristic is polygenic or that it is influenced by many genes, as well as the environment o Most human traits and diseases are polygenic 2. Genotype variation is created by sexual reproduction - Although siblings have same parents, they differ in many way o This occurs because the combination of genes in different due to random cell division which occurs prior to reproduction From calculating all the possible outcomes that can arise from the combination of 23 chromosomes, the result is one of 8 million possible outcomes and the parent themselves is one out 8 possible outcomes So there are 64 trillion possible combinations o The net outcome is a unique genotype is created at the moment of conception, and this accounts for the genetic variation in human species - The zygote grows via cell division o Sometimes there are mutations and most of the time they are benign Occasionally a mutation might produce an advantage or disadvantage in terms of survival and reproduction www.notesolution.com The evolutionary significance of this is complex, but it might lead to the mutated abilities or behaviour to spread through out the gene pool, because those who carry that gene are more likely to survive and reproduce o Industrial melanism The industrial pollution lead to the darkening of tree, thus moths or butterflies with mutations for darker color are more likely to survive, prior to the revolution they would be eliminated because they are easier to stop against pale backgrounds - How go genetic mutations lead to disease and why they remain in the gene pool? o Most are recessive, so when they are present alongside a dominant gene they do not get expressed, thus they survive in the gene pool and only those with two recessive genes get the disease Most dominant gene disorders are lethal and thus do not last in the gene pool 3. Genes affect behaviour - What determines the kind of person you are? o Factors that make you, you are influences by your genes and the environment you were raised in Behavioural genetics is the study how genes and the environment interact to influence psychological activity Behavioural genetics made an important contribution to the biological revolution by providing information to which extent biology influences the mild, brain and behaviour - Are genes responsible for human abilities like they are responsible for physical characteristics? o To which extent are the abilities influenced by nature and nurture? Research indicates that the gens lay the groundwork for many human traits and environment determines how they develop a. Behavioural genetic methods - Siblings are different even if they are raised in the same household o Is this because they have different genes or because the experience slightly different environments? www.notesolution.com
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