Development: The Contribution of Genes and Environment

Question 1

What is heritability?

Answer 1

A statistic that describes the proportion of observed variance in a population that is attributable to hereditary influence.

Change in the variety within environments will alter the heritability estimates

Behavioural geneticists use two major strategies to assess hereditary contributions to behaviour: selective breeding and family studies.

Question 2

Example of heritability

Answer 2

Heritability estimates the amount of genetic variation between individuals in a population beyond that accounted for by genetic determination.

Heritability of number of fingers on one hand
Genetic determination of number of fingers is HIGH.
Heritability of number of fingers is very LOW.

Question 3

Nature and Nurture

Answer 3

Everything about an individual – physical structure, intellectual capacity and personality characteristics – is a joint consequence of the interaction between genetic material (inherited from parents) and environments experienced throughout the lifespan.

Key Question: How are characteristics inherited, and to what degree are they influenced by environmental factors?

Question 4

Short history on genetic research

Answer 4

Gregor Mendel, a 19th century Austrian monk observed patterns of inheritance in pea plants.

Watson and Crick identified the structure of DNA – the basic component of hereditary transmission – in 1953.

Researchers have now mapped the entire genome of several species of plants and animals (including humans).

Question 5

What are the three key elements of nature and nurture?

Answer 5

Genotype – the genetic material an individual inherits

Phenotype – the observable expression of the genotype

Environment – all other aspects other than the genetic material itself.

Question 6

Genotype/ Phenotype Relations:

Relation 1: transmission of chromosomes and genes from parent to offspring;

Answer 6

23 pairs of chromosomes in every cell (total = 46), 23 single chromosomes in gametes;

Gender of new individual determined by sperm cell – female = XX (all eggs are X); male = XY (sperm are X and Y)

Question 7

Genotype/ Phenotype Relations:

Relation 2: relationship between child’s genotype and phenotype.

Answer 7

Although every cell identical, only some genes are expressed for each type of cell.

Many genes never expressed, some partially expressed – dominance patterns.

Two alleles (at least) for each gene.

Question 8

Genotype/ Phenotype Relations

Relation 3: impact of environment on child’s phenotype.

Answer 8

Continuous interaction of genotype and environment – a given genotype will develop differently.

Norm of reaction – the complete range of phenotypes that could result from a single genotype exposed to all environments in which it can survive.

Question 9

Example 1: Phenylketonuria (PKU)

Answer 9

Defective gene on Chromosome 12.

Cannot metabolise amino acid – phenyalanine.

Impaired brain development and mental retardation.

Question 10

Example 2: Parental contribution to environment

Answer 10

Parental contribution to environment – manner of interaction, general home environment, experiences they arrange, encouragement for particular behaviours and attitudes.

A child of a parent with musical ability likely to be exposed to more music.

Question 11

Genotype/ Phenotype Relations

Relation 4: the child as the source of their own development.

Answer 11

Three types of genotype: passive, active, evocative (Scarr & McCartney, 1983).

Question 12

Passive Genotype/ Environmental Correlations

Answer 12

Parents predisposed to be athletic may encourage their child to play vigorously, and to take an interest in sporting activities.

Question 13

Active Genotype/ Environment Correlations

Answer 13

Children actively seek out environmental niches that are most compatible with genetic predisposition.

Question 14

Evocative Genotype/Environment Correlations

Answer 14

Child’s genetically influenced attributes affect behaviour of others towards them. For example, smiley, active babies receive more attention and positive social stimulation than moody, passive ones.

Question 15

Genotype/ Phenotype relations and their influence over the lifespan

Answer 15

Evocative genotype effects someone throughout their whole life

Active genotype- activity increases with age

Passive genotype- people other than parents begin to gain larger influence (passive influence becomes less and less)

Question 16

Methodology to assess nature vs. nurture

Answer 16

Twin designs - comparisons of identical and fraternal twins

Consider: shared and non-shared family environment.

Adoption studies – comparisons of genetically related and unrelated children and parents.

Consider: adopted children higher IQ correlation with biological parents compared with adoptive parents.

Question 17

Rochester Longitudinal Study

Answer 17

Correlation between number of risk factors and lower IQ

Risk Factors (some examples):
Mother had history of mental illness
Mother did not attend High School
Mother had severe anxiety
‘Head of Household’ semi-skilled (SES)
Father not with family
20 or more stressful events through first 4 years
Child belongs to minority group
Few positive interactions between mother and child during infancy.

Question 18

Gene- environment interdependence

Answer 18

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Question 19

Gene-environement interdependence

Answer 19

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