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GeneticsGenetics
The Nature/Nurture DebateThe Nature/Nurture Debate
How great is the influence of genes or environment on our behavior, personality, biology, etc.?
The Nature Nurture DebateThe Nature Nurture Debate
Make two columns on a sheet of paper - 1) nature; 2) nurture Write characteristics you believe are mostly nature or mostly nurture in the appropriate columnIf the characteristic was nurture, what seemed to be the influences?
The Simple ViewThe Simple ViewBehavior = genes + environment
The Realistic ViewBehavior = genes + prenatal environment + parental influence + nutrition + family income + education + culture + traumas + chance …
Genetics and Genetics and BehaviorBehavior
Nucleus Chromosome Gene
Cell DNA
Gen
otyp
e &
Phe
noty
peG
enot
ype
& P
heno
type
Genes: Essential Genes: Essential DefinitionsDefinitionsChromosomes– threadlike structures made of DNA that
contain the genes
DNA (deoxyribonucleic acid)– complex molecule containing the genetic
information that makes up the chromosomes– has two strands-forming a “double helix”-
held together by bonds between pairs of nucleotides
Genes: Essential DefinitionsGenes: Essential Definitions
Genes– biochemical units of heredity that make up the
chromosomes– a segment of DNA capable of synthesizing a protein– The paradox 30,000 genes for 300,000 proteins
Genome– the complete instructions for making an organism– consisting of all the genetic material in its
chromosomes
Genes: Essential DefinitionsGenes: Essential Definitions
Genotype-The genetic constitution of an individual.
Depending on context, this may refer to the alleles at a single locus or to the complete set of genes.
Phenotype-Any measurable trait of an individual.
Phenotype results from an interaction between genotype and environment.
Genotypic Variation Is Created by Genotypic Variation Is Created by Sexual ReproductionSexual Reproduction
What determines the genetic uniqueness of individuals?– Gametes– Zygote
Mutations are experiments in selective advantage– Industrial melanism– Sickle-cell disease
- homozygotes - anemia, joint pain, swollen spleen, frequent severe infections, high rate of childhood death
- heterozygotes- basically normal blood function- resistant to malaria
Price for malarial resistance- homozygous sickle cell children
Sickle Cell Disease and Malaria
Sexual ReproductionSexual Reproduction
Combines gametes thereby creating new genotypeMay have evolved to outcompete parasites
Genes Affect BehaviorGenes Affect Behavior
Behavioral Genetics Methods:
– Twin Studies Compare MZ and DZ Twins:
– Adoption Studies:
Behavior GeneticsBehavior Genetics
Identical Twins– develop from a single
zygote (fertilized egg) that splits in two, creating two genetic replicas
Fraternal Twins – develop from separate
zygotes– genetically no closer
than brothers and sisters, but they share the fetal environment
Identicaltwins
Fraternaltwins
Samesex only
Same oropposite sex
Identical (monozygotic twins)Non-identical, fraternal (dizygotic twins)
Identical twins reared togethersame genes (relatedness of 1.0)same environment
Identical twins reared apartsane genes (relatedness of 1.0)different environment
Fraternal twins reared togetherhalf genes the same (relatedness 0.5)same environment
Fraternal twins reared aparthalf genes the same (relatedness 0.5)different environment
Nature v Nurture: Twin Studies
Jack Yufe: raised by Jewish father in Caribbean
Oskar Stohr: raised by catholic
grandmother in Nazi Germany
Nature v Nurture: Twin Studies
If we had identical twins reared apart could we separate the effects of phenotype, of genotype, and of the environment. In some cases this has happened.
Nature v Nurture: Twin Studies
Both like sweet liqueurs
Store rubber bands on their wrists
Read magazines from back to front
Dip buttered toast in their coffee
Have very similar personalities
MZ and DZ concordance MZ and DZ concordance ratesrates
Separated TwinsSeparated Twins
Twins StudiesTwins Studies
Comparing identical twins separated at birth
Twins studies movie
Environmental InfluencesEnvironmental Influences
Prenatal environment
Social and Environmental Social and Environmental Contexts Influence Genetic Contexts Influence Genetic ExpressionExpression
African Americans and Hypertension: a controversial theory
Gene expression as concerns child maltreatment and criminality is reflected in next slide.
Child Maltreatment, Criminality, and Gene Expression
Temperament and geneticsTemperament and genetics
Suomi genetic studies on rhesus monkeys– Two alleles of one gene:
the “short” version causes neurobehavioral deficits ONLY IF the infant monkey is raised with peers but without its motherThe “long” version causes no neurobehavioral deficits, regardless of rearing
– Maternal buffering?
Behavior GeneticsBehavior Genetics
Adoption studies– Are adopted kids more like their
biological relatives or their adopted relatives?
– General findings: adoptees more like biological parents than adopted parents in intelligence and personality/temperament