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Chapter 3

chapter 3 textbook note

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Dan Dolderman

Chapter 3 Genetic and Biological Foundations - researchers can now examine DNA to predict who will develop specific disorders and t understand how certain diseases are passed from one generation to the next - researchers have also identified genes that predispose people to be, among other things, outgoing, sociable, and intelligent - researchers recently developed techniques that allow them to turn specific genes on and of - changing the expression of a single gene can have profound effects even on complex behaviours such as social interaction - research at the biological processes that occur within the brain and body to produce experience, thought, emotion, memory, and behaviour - by building across the levels of analysis, we plan to demonstrate how psychological scientists conduct research to understand different questions related to mind, brain, and behaviour What is the genetic basis of psychological science? - within nearly every cell in the body is the genome for making the entire organism it is the master recipe that provides detailed instructions for everything from how to grow a gall bladder to where to place the nose on our face - whether a cell becomes part of a gall bladder or a nose is determined by which genes are turned on or off within the cell, and this is determined by cues form outside the cell - the genome provides the option, and the environment determines which option is taken - the term genetics is typically used to describe how characteristics are passed along through inheritance, but it also refers to those processes that are involved in turning genes off and on - chromosome structures within the cell body that are made up of genes - the typical human has 23 pairs of chromosomes half of each pair coming form each parent - genes in turn are components of a substance called DNA, which consists of 2 intertwined strands of molecules o sugar, phosphate, and nitrogen - the precise sequence of these molecules along the DNA strand specifies an exact instruction, through the production of RNA to manufacture distinct proteins - proteins, of which there are thousands of different types, are the basic chemicals that make up the structure of cells and direct their activities - gene the unit of heredity that determines a particular characteristic in an organisms - the process by which the gene produces RNA and then protein is known as gene expression, in that the gene is switched on - the gene has not only recipes for how to produce specific proteins, but is instructions for when to produce them environment determines all of this - the environment during its development likely causes a gene sensitive to temp to be expressed or switched on - gene provide options, and the environment determines which option is taken - each cell in human body contains same DNA, cut cells become specialized for different tasks or for having different effects when specific genes are expressed - genetic research providing a compelling new understanding of the biological basis of psychological activity Heredity involves passing along genes through reproduction - first clues to the mechanisms responsible for heredity were discovered by the monk Gregor Mendel around 1866 - there must be discrete units, now referred to as genes, that exist in two versions these two versions of a gene are known as alleles - if the alleles differ, one of them is dominant and the other is recessive - dominant genes a gene that is expressed in the offspring whenever it is present - recessive a gene that is expressed only when it is matched with a similar gene from the other parent - genotype and phenotype o the existence of dominant and recessive genes means that not all genes are outwardly expressed o genotype the genetic constitution determined at the moment of conception o phenotype observable physical characteristics that result form both genetic and environmental influences - polygenic effects o when there s a range of variability within a pop for certain characteristics, this indicates that the characteristic is polygenic, that is, influenced by may genes, as well as the environment o most human traits and diseases are polygenic Genotypic variation is created by sexual production - each ahs a specific combination of genes that differ in part due to random cell division that occurs prior to reproduction - reproductive cells from each parent divide to produce gametes, egg and sperm cells, that contain only one half of each pair of chromosome - one half o each parents chromosomes join in a random fashion - the fertilized cell, known as a zygote, contains 23 pairs of chromosomes, of each pair form the mother and the other half from the father rd - the 2 chromosomes in the 23 pair are the sex chromosomes, denoted X and Y due to their shape - females have two X chromosomes, whereas ales have XY - calculating all possible combinations of the 23 chromosomes indicates that this can result in some 8 million possible outcomes, the zygote is one of the 64 trillion possible combinations - the net outcome is that a unique genotype is created at the moment of conception, and this accounts for the genetic variation in the human species - the zygote grows when the chromosome duplicates and then the cell divides into two new cells with an identical chromosome structure - cell division is the basis of life cycle and is responsible or growth and development - errors in this process leads to mutations, most of which are benign and have little influences - a genetic mutation ma produce a selective advantage or disadvantage in terms of survival or reduction - mutations that lead to abilities or behaviours that are advantageous to an organisms ma spread through the gene pool because those who vary the gene are more likely to survive and reduce - there are ethnical issues related to genetic testing, such as whether the info should be available to employers and insurance companies Genes affect behaviour - the study of how genes and environment interact to influence psychological activity is known as behavioural genetics - behavioural genetics has made important contributions to the biological revolution, providing info about the extent to which biology influences mind, brain, and behaviour - any researcher that suggests that ability to perform retain behaviours are based in biology is controversial - a concern of psychological scientists is that the extent to which all of these characteristics are influenced by nature and nurture, by genetic makeup and the environment - people are born essentially like undeveloped photographs the image is already captured, but the way it eventually appears can vary based on the development process - the basic picture is there form the beginning - behavioural genetics methods o behavioural geneticists use two basic methods to assess the degree to which traits are inherited twin studies and adoption studies o twins studies compare similarities between different types of twins to determine the genetic basis of specific traits o monozygotic twins also called identical twins twin siblings who result form one zygote splitting into two, and therefore share the same genes o dizygotic twins fraternal or nonidentical twins twin siblings who result form two separately fertilized eggs o adoption studies compare the similarities between biological relatives and adoptive relatives o adopted siblings have similar home environments but different genes o the assumption is that similarities among adopted siblings have more to do with environment than genes o growing up in the same household has relatively little influence on many traits, such as personality o one interesting behavioural genetic study is to compare monozygotic twins who have been raised together or raised apart o this would seem the ideal way to test the relative contributions of gene and the environment o some critics have argued that most of the adopted twins were raised in relatively similar environments, in part issues adoption agents try to match the child to the adoptive home o some evidence suggests that twins raised apart are more similar than wins raised together o this would likely occur if parents encouraged individuality in twins raised together in emphasizing different strengths and interests o continued research using the methods of behavioural genetics is needed to provide additional insight into the relative influence of heredity and environment on individual behaviour - understanding heritability o heredity is the transmission of characteristics from parents to offspring by means of genes o heritability a statistical estimate of the fraction of observed measure of the overall amount of difference among people in a pop that is caused by differences in heredity o heritability refers to differences in a certain trait among individual, not to the trait itself
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