Is it all in the genes? NARTURE Heredity and Behavior Is it all in the genes? NARTURE

Behavioral Genetics- an interdisciplinary field that studies the influence of genetic factors on behavioral traits

Chromosomes and Genes Chromosomes are strands of DNA molecules that carry genetic information Every cell in the human body contains 46 chromosomes (except sex cells) 23 pairs (each parent) Zygote- a single cell formed by the union of a sperm and an egg Genes are the DNA segments that serve as the key functional units in the hereditary transmission

Why don’t family members look the same? Each parents 23 chromosomes can be scrambled in over 3 million different ways, yielding over 8 million configurations Homozygous condition –two genes in a specific pair are the same Heterozygous condition – two genes in a specific pair are different

Dominant Gene expressed when paired genes are different Recessive Gene one that is masked when paired genes are different Detached earlobe (D) Attached (R)

Genotype vs. Phenotype Genotype- a person’s genetic makeup Determined at conception/fixed Phenotype- how a person’s genotype is manifested in observable characteristics may change over time/modified by environmental factors

Polygenic Inheritance Characteristics that are influenced by more than one pair of genes 3/5 gene pairs determine skin color

Research Methods We can’t manipulate and do selective breeding on humans Family Studies- researchers assess hereditary influence by examining blood relatives to see how much they resemble one another on a specific trait Schizophrenic studies Also indicate whether or not a trait runs in a family

Twin Studies- researchers assess hereditary influence by comparing the resemblance of identical twins and fraternal twins with respect to a trait Identical Twins (monozygotic twins) emerge from 1 zygote that splits for unknown reasons Fraternal Twins (dizygotic twins) result when two eggs are fertilized simultaneously by different sperm cells, form two separate zygotes Useful because we can look at environmental conditions

Adoption Studies- assess heredity influence by examining the resemblance between adopted children and their adoptive parents Genetic/environmental influence on traits

Genetic Mapping- the process of determining the location and chemical sequence of specific genes on specific chromosomes Human Genome project Researchers seek to determine things such as the genetic basis for intelligence, extroversion, schizophrenia, musical ability, and other behavioral traits Virtually all behavioral traits tend to be polygenic and are shaped by many genes

The Evolutionary Bases of behavior

Darwin Natural selection Organisms vary in a variety of ways Some characteristics are heritable Variations in heredity are the basis of evolution Fitness- refers to the reproductive success of an individual organism relative to the average reproductive success of the population Variations in reproductive success are what actually fuels evolutionary change

Natural Selection posits that heritable characteristics that provide a survival or reproductive advantage are more likely than alternative characteristics to be passed on to subsequent generations and thus come to be ‘selected’ over time. Populations NOT individuals and a gradual occurance

Refinements to Evolutionary Theory Adaptation- an inherited characteristic that increased in a population(through natural selection) because it helped solve a problem of survival or reproduction during the time it emerged (preference for fatty foods) Inclusive fitness- sum of an individual’s own reproductive success plus the effects the organism has on the reproductive success of related others Self-sacrifice for the good of your genes (so they can survive)

Behaviors as Adaptive Traits Behavioral traits as well as physical are adaptive Behavioral maneuvers Hiding Trading sex for material goods that an aid survival