Download Chapter 3: Genetic Bases of Child Development

Chapter 3: Genetic Bases of
Child Development
Mechanisms of heredity
Behavior genetics
From genes to behavior
Mechanisms of Heredity
Genotype: the Human Genome
project sequenced the base pairs
(the DNA code) on all 23
chromosomes in 2003.
The human genome contains 2025,000 protein-coding genes.
Geneticists are rapidly figuring
out what they do.
PKU: non-carrier parents
PKU: inherited inability to metabolize phenylalanine
PKU: one carrier parent
PKU – two carrier parents
Behavior genetics: hypothetical example of
polygenic inheritance
3.1: Behavioral Genetics
Greater similarity among identical than fraternal twins is
evidence for hereditary influences
Plomin & Rowe’s (1979) twin study of sociability
(text, p. 60-61)
Plomin et al. (1997) adoption study (Kail, p. 362)
Reaction Range: a genotype can lead to a range of
phenotypes depending on the environment
People with PKU genotype who eat a normal diet will be mentally
retarded, but those who eat a special diet will have normal IQ
The Relation Between Genes and Environment
(adapted from Scarr & McCartney, 1983)
conception
Gene expression
X
experience
evocative & active
phenotype
passive
Gottlieb’s developmental systems model
Identical twins’ intelligence test scores 6-24 months
Relationship between childhood maltreatment, MAOA activity and
antisocial behavior (gene-environment interaction) (Caspi et al., 2002)