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The Nature and Nurture of Behavior

• Genes

• Explaining Similarity

• Explaining Differences

• Environmental Differences

• Gender

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The Nucleus

• Chromosomes

• Genes

• Deoxyribonucleic acid (DNA)

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Chromosomes

• Rod shaped structures found in the center of the nucleus of every cell in the body.

• Each sperm and each ovum contains 23 chromosomes.

• The chromosomes contain the genes.• The fertilized egg (zygote) and all the body cells

that develop from it (except the sperm cells and the ova) contain 46 chromosomes.

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KaryotypeA photograph of a cell’s chromosomes

arranged in pairs according to size

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Genes

• The basic unit of genetic information

• They determine the nature and the function of the cell.

• The human genes (about 140,000) are referred to as the human genome.

• A genome is the full set of genes in each cell of an organism.

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A Portion of a DNA Molecule

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DNA

• The substance that genes are composed of that determines the nature of each cell and how it will function.

• At each level of the spiral or rungs of the ladder are particular chemical pairs. The arrangement of these pairs along the DNA molecule determines which kind of proteins that will be formed in the cell.

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Terms• Gametes:

Sex cells (ovum or sperm)

• Diploid cells:

Cells having 2 copies of each chromosome

• Haploid gametes:

Gametes having 1 copy of each chromosome

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Meiosis• Meiosis takes place in the testicles and ovaries.• A diploid cell (having 2 copies of each

chromosome) undergoes a special form of cell division to create haploid gametes (having 1 copy of each chromosome).

• An egg and a sperm fuse together to form a new diploid cell called zygote (a process called fertilization)

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Mitosis• In the first step of mitosis, all chromosomes are

copied, so that instead of 2 copies, the cell briefly has 4 copies of each chromosome.

• Shortly afterwards, the cell divides in half, resulting in two cells each has a complete copy of the genetic information.

• These cells grow larger and eventually undergo mitosis.

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Gregor Mendel (1800s)

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Genotype

The genetic makeup of a given individual

Recessive Gene

The gene pair that determines a trait in an individual only if the other member of that pair is also recessive

Phenotype

The traits that are expressed in the individual

Dominant Gene

One gene of a gene pair that will cause a particular trait to be expressed

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Stop and Discuss• Gametes• Zygote• Monozygotic twins• Dizygotic twins• Diploid cells• Haploid gametes

• Chromosomes• Genes• DNA• Meiosis• Mitosis

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Celera GenomicsThe Human Genome Project

• In June 26, 2000, they both made an announcement that the “correct alphabetical order of the 3.12 billion letters” of the human genome had been mapped.

• It will be many years before the incredibly complex functions of the genome in making and maintaining a living human being are fully understood.

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Genetic Engineering

• Alteration of Human Genes

• 1- Gene Therapy

• 2- Germ-line Genetic Alterations

Germ-line Genetic Intervention

• 3- Genetic Enhancement

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1- Gene Therapy• Genetic alteration of somatic cells to treat

disease.• Researchers inject genes that are targeted to

treat a particular disease in to a patient’s blood stream.

• When the genes arrive at the site of the defective genes, they produce chemicals that can treat the problem.

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2-Germ-line Genetic Alteration

• Can correct problems for unborn individuals and future generations.

• It targets the genes in the reproductive cells – the egg and the sperm that combine the DNA to conceive a new human.

• Scientist might detect defective cells soon after conception, removing them from the mother and placing them in a test-tube culture.

• Gene therapy could be employed to correct the defects in the cells.

• The result could be cloning. Parents could some day customize their children.

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3-Genetic Enhancement

• Non therapeutic genetic alteration

• An attempt to enhance an already healthy genetic makeup by inserting a gene for improvement (e.g. height, intelligence, eye color)

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What Do You Think?

Genetic Engineering

Gene TherapyGerm-Line Genetic

AlterationsGenetic enhancement

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Cloning

• Producing genetic replicas of the organism

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Stop and Discuss

• In your opinion, how ethical are these issues?

1- Gene therapy

2- Germ-line genetic alteration

3- Genetic enhancement

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Universal BehaviorsEvolutionary Psychology

Evolutionary Psychology• The study of the evolution of behavioral

the mind using principles of natural selection

Natural Selection• The traits that contribute to reproduction

and survival will most likely be passed on to succeeding generations.

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Universal BehaviorsEvolutionary Psychology

• Belyaev (Tame Foxes)

• Mutation

A random error in gene replication that leads to a change in the sequence of nucleotides; the source of all genetic diversity.

• Sexuality

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David Bussand the International Team

(1994)• 50 scientists studied:

10,000 people

in 37 cultures

in 6 continents

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Human Sex Differences Are Universal

• Males• Promiscuous• Undiscriminating• Competitive and

concerned about dominance

• Prefer beauty and health

• Like sexual novelty

• Females• Devoted and faithful• Cautious• Less competitive

• Prefer resources and social status

• Like stability and security

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Innate Human Characteristics

• Infant Reflexes

• An Attraction to Novelty

• A Desire to Explore and manipulate objects

• An Impulse to play and Fool Around

• Basic Arithmetic Skills

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Language Acquisition DeviceInnate Mental Module

Noam Chomsky• Children in different cultures go through

similar stages of linguistic development.• Children combine words in ways adults

never do.• Adults don’t consistently correct their

children’s syntax.• Even retarded children develop language.• Infants can derive simple linguistic rules.

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Explaining DifferencesBehavior Genetics

Behavior Genetics

• The study of the relative power and limits of genetic and environmental influences on behavior

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Twin Studies

• 13,000 pairs of Swedish twins, 7000 Finnish twin pairs, 3810 Australian twin pairs

Identical twins are more similar than fraternal twins on both extroversion & neuroticism

• Battery of questionnaires to 850 U.S. twins

Identical twins are more similar inabilities, personality traits, & interests.

Reported being treated alike

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Separated Twins

• The Jim Twins

Similar in:

brain waves

voice intonation

interests

heart rate

personality

intelligence

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Adoption Studies

• People who grow up together, whether biologically related or not, do not much resemble one another in personality.

• Adoptee’ traits bear more similarities to their biological parents than to their care-giving adoptive parents

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Temperament Studies

Traits such as

excitability – whether the baby is intense, reactive, fidgety, easy going, or quiet

tend to remain steady in later years

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Group Differences

Of our genetic differences– Only 6% are among races– Only 8% are differences among groups

within a race– The rest – over 85% - are individual

variations within local groups– Some traits are highly heritable:

• Weight, height, and intelligence

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The “Obese” Gene

• Obese gene causes fat cells to produce leptin.

• Leptin travels through blood to hypothalamus (regulates appetite)

• Leptin reduces appetite

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The Function of the Protein Leptin

• Reduces appetite

• Speeds up metabolism

• Makes people more active

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Why Do People Gain Weight Rapidly?

• Secretion of leptin is impaires

• May produce plenty of leptin but their body does not respond to it.

• Tendency to store calories which have a survival advantage.

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Gene-Environment Interaction

“Heredity deals the cards; environment plays the hand.”

Psychologist Charles L. Brewer

(1990)

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Environmental Influence

• Prenatal Environment

• Experience and Brain Development

• Peer Influence

• Culture

• Gender

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Prenatal Care

• Diet

• The father’s involvement

• Age of mother

• Illness of mother

• Drug use

• Alcohol

• Teratogens

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Experiences and Brain Development

• Rosenzweig and Krech’s experiment on rats:– Those living in the enriched environment

developed a thicker and heavier brain cortex.– Experience preserves our activated

connections while allowing the unused connections to degenerate

Use it or lose it

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Parents and Peers are ComplementaryHoward Gardner (1998)

“Parents are more important when it comes to education, discipline, responsibility, orderliness. Charitableness, and ways of interacting with authority figures. Peers are more important for learning cooperation, for finding the road to popularity, for inventing styles of interaction among people of the same age. Youngsters may find their peers more interesting, but they will look to their parents when contemplating their own futures.”

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Culture

• Variation Across Cultures

• Variation Over Time

• Culture and Child Rearing

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Gender

• The Nature of Gender– X chromosome– Y chromosome– Testosterone

• The Nurture of Gender– Gender role

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What Is the Role of Parenting?

1- Do parents really produce future adults with a wounded child within by being irresponsible?

2- Should we blame our parents for our failings?

3- Should we shame the parents of troubled children?

4- Should parents be given less credit for children who turn out great?

5- What is the role of parents?