ITP - Topic 5 - Genetics PDF

Chapter 5 GENETICS PSYCH01X- Introduction to Psychology  Learning Objectives: At the end of the session, the learners will be able to: 1. Define Behavioral Genetics. 2. Differentiate the hereditary as well as the environmental determinants of behaviors; 3. Differentiate Genotype from Phenotyp...

Chapter 5 GENETICS PSYCH01X- Introduction to Psychology  Learning Objectives: At the end of the session, the learners will be able to: 1. Define Behavioral Genetics. 2. Differentiate the hereditary as well as the environmental determinants of behaviors; 3. Differentiate Genotype from Phenotype 4. Identify different Mutations and Genetic Abnormalities  NATURE VS. NURTURE NATURE NURTURE Heredity (Nature) Environment (“Nurture”) Transmission of physical and All external conditions that affect psychological characteristics from development parents to their children through genes DEFINITION: GENETICS Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms. Genetics arose out of the identification of genes, the fundamental units responsible for heredity. Genetics may be defined as the study of genes at all levels, including the ways in which they act in the cell and the ways in which they are transmitted from parents to offspring. What is Behavior genetics? It is a field of psychology that involves the study of biology. It seeks to determine the extent to which our behavior and the rest of our individual differences can be attributed to the genes. Behavior Geneticist contributes the understanding of the influence of heredity (nature) on personality traits, such as aggression, shyness, etc. on mental abilities, and even on psychological disorders, all of which have, for so long a time, been attributed to the environment (Nurture) Heritability Heritability refers to the extent to which the differences among people are attributable to genes. Heritability can be difficult to understand, so there are many misconceptions about what it can and cannot tell us about a given trait: Heritability does not indicate what proportion of a trait is determined by genes and what proportion is determined by environment. So, a heritability of 0.7 does not mean that a trait is 70% caused by genetic factors; it means that 70% of the variability in the trait in a population is due to genetic differences among people. Knowing the heritability of a trait does not provide information about which genes or environmental influences are involved, or how important they are in determining the trait. Heritable is not the same as familial. A trait is described as familial if it is shared by members of a family. Traits can appear in families for many reasons in addition to genetics, such as similarities in lifestyle and environment. For example, the language that is spoken tends to be shared in families, but it has no genetic contribution and so is not heritable. Heritability does not give any information about how easy or difficult it is to change a trait. For example, hair color is a trait with high heritability, but it is very easy to change with dye. Genes: Our Codes for Life Chromosomes containing DNA (deoxyribonucleic acid) are situated in the nucleus of a cell. Genes: Our Codes for Life Segments within DNA consist of genes that make proteins to determine our development. Genome Genome is the set of complete instructions for making an organism, containing all the genes in that organism. Thus, the human genome makes us human. Genes 101 Dominant Gene – Member of a gene pair that controls the appearance of a certain trait. Recessive Gene - Member of a gene pair that controls the appearance of a certain trait only if it is with another recessive gene. Genotype/Phenotype Genotype Phenotype the set of genes you inherit, your unique how that set of genes is expressed as a result of blueprint the environmental stresses the observable characteristics GENES 101 Polygenic Inheritance – Process by which several genes interact to produce a certain trait; responsible for our most important traits. Twin Biology Sexual Reproduction and Genetic Transmission Chromosomes Single molecule of DNA, thousands of genes 23 + 23 = zygote Genes segments of DNA, double helix, ladderlike blueprint for synthesis of protein molecule units of heredity GENES, DNA AND CHROMOSOMES Cell Division: Somatic Cells Mitosis for somatic (body) cells each cell replicates itself, then divides result is two cells identical to original Cell Division: Germ Cells Meiosis for germ cells replication with 3 processes to ensure resulting cell is nonidentical to germ cells (genetic diversity: chances are 1/70 trillion) 2 steps of division crossing over random pairing during 2nd division monozygotic vs. dizygotic twins Heritability of Intelligence: History Francis Galton’s Eminent Persons Study tested idea that differences in intellectual achievement was due to genetic differences basic flaw in logic is that eminent people also shared similar environment as well as gene pool first to use adoptive method in study of boys adopted by RC Popes; found little evidence that environment affected eminence Recommendations made for selective breeding, as they were to be made later by Hitler Heritability of Intelligence: Kinship Studies Twin Methods correlations among IQs of pairs of people related to different degrees, e.g., identical twins, dizygotic twins, siblings, Adoptive Methods correlations among pairs of people who share an environment but not genes, e.g., adopted child and biological child Mutations/Genetics/Chromosomal Abnormalities Mutations are errors in the process of gene replication; can be positive but usually negative Down Syndrome ; trisomy 21 (chromosomal error) Phenylketonuria (PKU- defective recessive gene) Klinefelter syndrome (sex-linked chromosomal abnormality) Sickle-cell anemia (recessive gene) Turner’s Syndrome XYY Edward’s Syndrome; Trisomy 18