PPE 3003 1st Edition Exam 3 Study Guide Lectures 8 10 Lecture 8 1 Understand the hierarchy of the genome e g Chromosomes are made up of what Genes are made up of what The genome is the complete set of genes an organism processes It contains between about 20 000 and 30 000 genes All genes are located on 23 pairs of chromosomes Chromosomes are made up of tightly coiled DNA Genes are the basic physical and functional unit of heredity and is made up of DNA Every person has two copies of each gene one inherited from each parent The nucleus of each cell with the exception of red blood cells sperm and eggs contains two sets of the human genome one from the mother and one from the father The body has 100 trillion cells with 100 trillion copies of human genome 2 Know the difference between a phenotype and a genotype The genotype is an organism s genetic information The phenotype is an organism s observable characteristics such as height weight and hair color 3 Know the goals of behavioral genetics The goals of behavioral genetics is to determine what percent of trait differences is due to genetics and what percent is due to environment how do genes and environment interact and what environmental effects are important 4 Be able to define and describe heritability and enviromentality Heritability is how much an individual difference is explained by genetics It is also a statistic that refers to the proportion of observed variance in a group of individuals that can be accounted for by genetic variance The formal definition is the proportion of phenotypic variance that is attributed to genotypic variance Environmentality is how much of an individual difference is due to environment 5 Be able to recognize examples of common misconceptions about heritability A common misconception is that heritability can be applied to a single individual because it cannot Heritability refers only to differences in a sample or population not an individual Another misconception is that heritability is a constant but it is really nothing of the sort it does not generalize across persons and places Also a misconception is that heritability is an absolutely precise statistics it is not true Instead heritability is an estimate of the percentage of phenotypic differences due to genetic differences It is not precise nor is it eternally fixed 6 Be able to list define and describe the four methods used in behavioral genetics The four methods used in behavioral genetics are selective breeding in dogs family studies twin studies and adoption studies Selective breeding is identifying the dog that posses the desired characteristic and having them mate only with the dogs that also possess the characteristic Many of the qualities they wish to give to specific dog breeds are moderately to highly heritable Some heritable qualities are physical traits such as size coat of hair and ear length Some are behavioral and considered personality traits such as sociable agreeable aggressive and desire to please Family studies correlate the degree of genetic relatedness among family members with the degree of personality similarity and capitalize on the fact that there are known degrees of genetic overlap among family members Parents share 50 of genes and siblings share 50 of genes Grandparents and grandkids share 25 of genes and aunts and uncles share 25 with nieces and nephews First cousins share 12 5 If a personality characteristic is highly heritable then family members with greater genetic relatedness should be more similar to each other than are family members with less genetic relatedness If a personality characteristic is not at all heritable then even family members who are less genetically related to each other These cannot be definitive Twin studies are an estimate heritability by gauging whether identical twins who share 100 of their genes are more similar to each other than are fraternal who share 50 of their genes Twin studies especially twins reared apart have received tremendous media attention Weird coincidences seem to happen with unusual regularity in the course of studying twins Twins occur only 1 in 83 births Adoption studies are the most powerful method because it examines the correlation between adopted children and their adoptive parents with whom they share no genes If there is a positive correlation between adopted children and adoptive parents then there is a strong environmental influence If there is a positive correlation between adopted children and genetic parents then there is a genetic influence 7 Know the advantages and limitations of each of the four methods used in behavioral genetics In selective breeding it can infer heritability if selective breeding works A limitation to this method is that it is unethical to conduct on humans For family studies an advantage is that is provides heritability estimates but a disadvantage is that it violates equal environments assumption Twin studies allow for both heritability and environmental estimates but sometimes violate equal environment assumption Adoption studies allow for both heritability and environment estimates and gets around the issue of equal environment assumption but still has the problem of selective placement of children not being representative of the population 8 Know the difference between monozygotic and dizygotic twins Monozygotic twins or identical twins come from a single zygote and share a single fertilized egg They also share 100 of their genes and can only be same sex Dizygotic twins or fraternal twins come from two separately fertilized eggs and two zygotes They share 50 of their genes and can be same sex or opposite sex 9 Know the major findings of behavioral genetics that were discussed in class They found that for the Big Five extraversion 40 60 and neuroticism 30 54 were highly and moderately heritable Sexual orientation is controversial and a developing area But genes are modest and indirect influences on adult sexual orientation with about 20 67 heritability Attitudes and preferences have a lot of variance in heritability For example some shoe high heritability such as traditionalism with 34 63 heritability while others such as religious beliefs show low to no heritability As of right now researchers do not agree or know exactly what makes an attitude heritable or not Drinking and smoking are also findings Drinking is thought to be related to sensation seeking extraversion and neuroticism While drinking alcohol is 36 56 heritable
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