Exam 3 Learning Objectives Genetics Heritability Lecture 8 1 Be able to define genome Genome is the complete set of genetic information for an organism It can be thought of as a blueprint or set of instructions for building an organism Each species has its own genome The human genome is spread across 23 chromosomes which hold our DNA or genetic code Very small number of genes are different across people 2 Understand the hierarchy in the genome e g Chromosomes are made up of what Genes are made up of what Genome Chromosomes Genes DNA Genome a full set of chromosomes all the inheritable traits of an organism Chromosomes any of several threadlike bodies consisting of chromatin that carry the genes in a linear order the human species has 23 pairs Genes the basic physical unit of heredity a linear sequence of nucleotides along a segment of DNA that provides the coded instructions for synthesis of RNA which when translated into protein leads to the expression of hereditary character DNA an extremely long macromolecule that is the main component of chromosomes and is the material that transfers genetic characteristics in all life forms 3 Be able to define behavioral genetics Behavioral genetics Studies to what degree are individual differences due to genetic environmental factors 4 What are the controversies surrounding behavioral genetics Controversy surrounding behavioral genetics o Eugenics A pseudoscience with the stated aim of improving the genetic constitution of the human species by selective breeding o Genetic determinism refers to the idea that all human behavior is innate determined by genes brain size or other biological attributes o Genes environment interact 5 What are the three major questions asked by behavioral geneticists What causes variability in a trait genes vs environment What environmental effects are important e g parents teachers peers How do genes and environment interact 6 What is heritability Heritability How much an individual difference is explained by genetics 7 Be familiar with the misconceptions about heritability and be able to recognize examples Heritability o CANNOT be applied to single people A single individual s height for example is not 10 due to their environment It is more accurate to say that the variation between people in height is 10 due to the environment o Is NOT constant unchangeable Heritability only applies to a population at one point in time The more similar the environment between people the higher heritability will be o Is NOT a precise statistic Only as good as the sample used 8 Be able to list and define the four methods used in behavioral genetics Selective breeding Process of breeding plants and animals for particular genetic traits or in order to produce a specific type of organism with particular identical genetic traits typically for research Family studies involves examining the changes individuals undergo in life and understanding how these fit into complex family dynamics Twin studies research involving twins that evaluates the relative contributions of environment and genetics to some attribute Particularly frequently consists of comparing the traits of fraternal and identical twins and comparing twins of both kinds who have been raised together or apart Adoption studies are one form of clinical genetic study designed to evaluate genetic and environmental influences on phenotype In adoption studies the index cases and controls are adoptees 9 Know advantages and disadvantages associated with each method from behavioral genetics Selective breeding o Can t be done ethically with humans o Only works if a desired trait is heritable o If selective breeding for a trait is successful the trait is at least somewhat genetic Family studies Twin studies Adoption studies o Correlates genetic similarity w personality similarity o If trait is heritable more genetic relatedness more similarity on traits o Problem Families share genes and environment Family studies are never definitive 10 Know the difference between monozygotic and dizygotic twins Monozygotic twins o Share a single fertilized egg a single zygote monozygotic o Share 100 of their genes Dizygotic twins o Come from two separately fertilized eggs two zygotes dizygotic o Share about 50 of their genes 11 Be able to compute heritability if I give you the correlations for monozygotic and dizygotic twins Estimate heritability twins o Are identical monozygotic MZ twins more similar than fraternal dizygotic DZ o If MZ twins are more similar than DZ twins on a given trait due to heritability Example Neuroticism o DZ twins correlated at 18 o MZ twins correlated at 41 Heritability 2XDifference in correlation o Heritability 2 41 18 o Heritability 2 23 46 o Heritability 46 12 Which kind of study generally gets higher heritability scores Adoption or twin studies Twin studies 13 What is nonadditive genetic variance Nonadditive genetic variance differences caused by interactions between genes o Genes influence traits in a non additive fashion either share 100 of your genes and share the same genotype MZ twins or you don t everyone else o MZ s with same genotype are likely to be similar everyone else may share similarities with family members but will be essentially different o Biologocial siblings Non MZ twins are not very much more similar to each other than are adoptive siblings 14 Be familiar with the heritability of the extraversion neuroticism drinking and alcoholism Drinking related to o Sensation seeking o Extraversion o Neuroticism Drinking 36 56 Alcoholism 50 71 15 Know that any variance not accounted for by genetics is accounted for by environment if height is 90 heritable it is 10 environmental 16 Know the difference between shared and non shared environments and know which type of environments has a larger influence on personality Nonshared Shared environment siblings share environment siblings do not share bigger effect 17 Be able to define and recognize examples of an environment genetic interaction Environment genetic interaction People with different genes show different behaviors in the same environments o Ex Some individuals cannot study in an environment with noise yet some can 18 Be able to describe and recognize examples of the three types of genotype environment correlations People with different genes are exposed to different environments o Passive Parents provide both genes and environment yet children do nothing to obtain that environment Example Parents with high
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