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Chapter 3


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Dan Dolderman

What Is the Genetic Basis of PsychologyGenetics in PsychologyThe processes involved in turning genes on and off Environment affects our genes how they are expressed and therefore how they influence our thoughts feelings and behaviour but genetic tendency often determine the environment we select for ourselves so biology and environment mutually influence each other Details in notes below Within every cell in the body is the genome genetic makeup for making the entire organismEach cell has a certain option what they do but this depends on the environment because the environment determines which options are taken what genes are turned on and off in a cellWithin each cell are chromosomes structures made of genes Typical human has 23 pairs of chromosomes half of each pair coming from each parent Genes are components of DNA and the sequence of the genes produces a certain protein which carries out a specific task The environment determines what protein is produced and whenAs mentioned above although each cell in the body contains the same DNA cells become specialized depending on which genes are expressed Gene expression determines bodys basic physical makeup and also specific developments throughout life and is involved in all psychological activity ex Learn fall in love etc The Human Genome Project Map out entire structure of DNATo identify the precise order of molecules that make up each of the thousands of genes on each of the 23 chromosomes Humans have just over 20000 genes Humans complexity is not due to the number of genes but rather to how these genes are expressed and regulatedWith the Human Genome Project researchers are now comparing different individuals genomes to how they vary specifically how variations in individuals genes determine whether someone is likely to develop specific disease or have some special abilityHeredity Involves Passing Along Genes through ReproductionGregor Mendel was the first to discover clues to the mechanisms responsible for heredity transmission of characteristics from parents to offspring by means of genesHe developed selective breeding that controlled which plants bred with which other plants He cross pollinated two different colored flowers purple and white to see what colour flower would be produced First generation either completely white or completely purple Second generation plants were purple flowers were produced 75 of the time because plants contained separate units genes existing in different variations colours Purple was dominant gene expressed in offspring whenever present and white was recessive only expressed when matched with a similar gene from the other parentGenotype Organisms genetic makeup determined at the moment of conception Phenotype Observable physical characteristics resulting from both genetic and environmental influences ex Skin colour may vary due to the sun environmental influence Polygenic Effects When a population displays a range of variability for a certain characteristics Ex Height or intelligence This variety of for example skin colour phenotype is not the end product of a single dominantrecessive gene pairing genotype but rather shows the effects of multiple genesGenotypic Variation is Created by Sexual ReproductionSiblings are different from each other hair colour eye colour height personality etc due to the specific combination of genes determined by random cell division before reproduction In each parents reproductive cells divide to produce gametes the egg and sperm cells each of which contains half of every chromosome pair After one of each cell combines a zygote is formed There are about 8 million combinations of the 23 chromosomes are possibleThe zygote grows through cell division which is the basis of lifeErrors can occur which lead to mutations Most have little to no influence but some mutations can be adaptive mutations that help survival so will be passed onto future generations or maladaptive ones that can lead to disease and possibly deathRecessive maladaptive genes do not interfere with most peoples health only when they are dominant do they affect people Genes Affect BehaviourBehavioural Genetics Study of how genes and environment interact to
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