Lecture 3 HEREDITY & THE ENVIRONMENT Visiting Assistant PROFESSOR YEE-SAN TEOH Department of Psychology National Taiwan University 1 Unless noted, the

Lecture 3 HEREDITY & THE ENVIRONMENT

Visiting Assistant PROFESSOR YEE-SAN TEOH

Department of Psychology

National Taiwan University 1

Unless noted, the course materials are licensed under Creative Commons Attribution-NonCommercial-ShareAlike 2.5 Taiwan (CC BY-NC-SA 3.0)

GENERAL PSYCHOLOGY

GENETIC FACTORS DETERMINE ONLY AN PERSON’S

GENOTYPE (STARTING POINT), BUT GENES DO NOT DETERMINE HOW THE PERSON WILL END UP

(PHENOTYPE)

HEREDITY

WHAT IS THE GENOTYPE?

WHAT IS THE PHENOTYPE?

THE GENOTYPE

THE PROCESS OF GENETIC TRANSMISSION WHERE THE GENES ARE

Within each cell nucleus are chromosomes…

On which genes containing the genetic code are located

Chromosomes are bound by molecules of DNA.

THE PROCESS OF GENETIC TRANSMISSION MEIOSIS & SEXUAL REPRODUCTION

Chromosome combinations occur during the formation of sperm and egg cells.

Crossing over – exchange of genes on homologous chromosomes.

Union of sperm and ovum = 23 male & 23 female chromosomes

THE PROCESS OF GENETIC TRANSMISSION MEIOSIS IN DEPTH

Process of cell division.

23 chromosome pairs are split/halved.

Halving enables union of sperm and egg.

Result is 23 from the sperm combines with 23 from the egg to produce 46 for new human being.

HOW TRAITS ARE TRANSMITTED

Since genes are located on chromosomes, they also come in pairs.

Each gene occupies a position on each half of the chromosomal pair.

2 identical paired genes = homozygous

2 different paired genes = heterozygous

A specific gene has alleles which produce variations of that gene.

Wikispaces: KKPM


Expressions of heterozygous combinations:1.Dominant – one gene will govern outcome over other gene. E.g. Dimples vs no dimples

2.Recessive – allele that will affect phenotype only if it matches allele of partner gene (inherits same recessive allele from each parent). E.g. Baldness only if the gene pair is homozygous for the recessive trait.


Expressions of heterozygous combinations:3.Codominant – both genes affect phenotype. E.g. Blood type A + Blood type B = AB

4.Incomplete dominance – person with 2 different alleles will have a phenotype that’s intermediate. E.g. Serotonin transporter gene located on chromosome 17 can have alleles of different length, long allele has incomplete dominance over short.

POLYGENIC INHERITANCE

The expression of some traits is controlled by more than one gene pair.

Specific genetic patterns create a risk of developing a certain trait/disease.

Example: Bipolar disorder and schizophrenia are much

more likely if a person inherits a certain genetic pattern (not just one gene).

INTERACTION OF GENES

Very few traits are specified by single genes – most traits depend on a combination of genes.

Many behaviors or characteristics are influenced by multiple genes.

A gene may influence more than one trait. Modifier genes affect the expression of other

genes.

Online Mendelian Inheritance in Man (OMIM)

Access the website for genetic database.

GENE EXPRESSION

Whether or not a gene will be active, depends on many factors that modify the biochemical environment inside the cell, turning genes “on” or “off”.

What can alter gene expression?

1. ENVIRONMENT JUST OUTSIDE THE CELL…OTHER CELLS

2. TIMING – SOME GENES ACTIVE EARLY VS LATE

C. OVERALL ENVIRONMENT & BEHAVIOR

GENE-ENVIRONMENT INTERACTION IS BI-DRECTIONAL

Bidirectional Interaction between Genetic Factors and Context

(a)Environment & experience impacts gene expression.(b)Genetic factors shape what person experiences.

THE FIELD OF HUMAN BEHAVIOR GENETICS

SOME MISCONCEPTIONS OF BEHAVIOR GENETICS….(RUTTER, 1992; 2006)

Genes limit potential. Strong genetic effects = insignificant

environmental influences. Genetic influences diminish with age. Genes regulate only static

characteristics.

HEREDITY & THE ENVIRONMENT

HOW DOES THE ENVIRONMENT INFLUENCE THE EXPRESSION OF GENES?

ENVIRONMENT

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RANGE OF REACTION (GOTTESMAN, 1963; PLOMIN, 1995)

Heredity does not rigidly fix behavior.

It establishes a range of possible developmental outcomes that may occur in response to different environments.

People with different genetic make-ups have different ranges of reaction.

Range of reaction is particularly useful for understanding the variation in complex behaviors.

EXAMPLE:

An enriched, stimulating environment can substantially improve a child’s intellectual ability.

However, each child’s genotype determines the limits within which his/her ability will vary.

Source: From "Genetic Aspects of Intelligent Behavior " (p. 255), by I. I. Gottesman, in N. R. Ellis (Ed.), Handbook of mental deficiency: Psychological theory and research, 1963, New York: McGraw-Hill.

AN IMPORTANT INFLUENCE ON THE GENE-ENVIRONMENT INTERACTION…

Developmental Stage Critical periods: developmental stages where

the impact of the environment on development is most significant.

Example: Kids with PKU must be placed on a special

diet (low in phenylalanine) immediately after birth to prevent mental retardation (Baumeister, 1967)

HOW DOES GENETIC MAKEUP SHAPE ONE’S ENVIRONMENT?

EXAMPLES….

METHODS OF STUDYING INDIVIDUAL DIFFERENCES

1. Compare adopted children with their biological & adoptive parents.

- Similarity to adoptive parents = environment.

- Similarity to biological parents = shared genetic makeup.

- Studies by Moffitt & Caspi, 2006; Rutter, 2006)

- Comparison of biological siblings and adopted children in same home.

2. Compare identical and fraternal twins raised together in the same home.

- If identical twins show more resemblance on a trait than fraternal twins do = genetic influence

- If both identical and fraternal twins show similar strength of resemblance on a trait = environment

3. Compare shared & non-shared environments

- Identical twins have more shared environments – (i) identical genes & inherited predispositions,

(ii) similar treatment by parents, (iii) evoke similar responses from others, (iv) select more similar

settings/companions/activities (Scarr, 1996).

- Fraternal twins & siblings are more likely to have separate experiences and activities.

- Towers et al. 2003 - similarity caused by shared home declines with age, more niche picking.

3 PRINCIPLES OF EVOLUTION OF BEHAVIOR THROUGH NATURAL SELECTION

(a) There must be a variation among the individuals within a population.

(b) Certain of the variants must survive and reproduce at higher rates than others.

(c) The traits associated with this superior survival and reproduction must be passed from parents to offspring.

CopyrightsPage Work License Author/Source

3 National Taiwan University YEE-SAN TEOH

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National Taiwan University YEE-SAN TEOH

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Wikispaces: KKPMhttp://kkpm.wikispaces.com/Genetics+and+Evolution 2012/03/17 visited

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CopyrightsPage Work License Author/Source

20 National Taiwan University YEE-SAN TEOH

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This graph is adapted from Gottesman,1963http://www.archive.org/details/handbookofmentaL00elli and out of copyrigh so belongs to public domain.

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Documents

Lecture 3 HEREDITY & THE ENVIRONMENT Visiting Assistant PROFESSOR YEE-SAN TEOH Department of Psychology National Taiwan University 1 Unless noted, the