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

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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