Environmental and genetic interaction?Presentation Transcript
Genetics and Prenatal Development D. Messinger, Ph.D. Messinger Psychology of Infancy
What are the advantages (name some forms of genetic transmission) and disadvantages of thinking of genes as blueprints?
How do environmental and genetic influences interact during prenatal development (provide examples)?
What is the difference between transactional and a behavioral genetics approach to gene * environment interactions?
Nature – genetics
Genes as blueprint
Nurture – environment
Genes, environment, and their interaction accounting for outcome?
Messinger Back to developmental models Who believes in?
Bits of DNA, protein, in each cell
contain information on cell functioning, production, and reproduction
Larger groupings of DNA
All non-gamete cells in the body have 23 pairs of chromosomes
Half of each pair came from each parent
Chromosomes Messinger In vitro Ordered by karotyping
Human genome project
identify all the approximately 30,000 genes in human DNA,
determine the sequences of the 3 billion chemical base pairs that make up human DNA,
99% (of nucleotide bases) are the same in all people
Detailed description Messinger
UM Genetic Researchers Publish New Autism Findings
Geneticists at the University of Miami Leonard M. Miller School of Medicine, havelocated a region of chromosome 12 that they believe harbors a new gene related to autism. Molecular Psychiatry.
Defects in many as 20 different genes may cause autism in a single individual, and these genes are not necessarily the same ones that cause the disease in another autism patient, she said.
The researchers screened the entire genome -- the body's genetic blueprint -- of 26 extended families with at least two members with autism, looking for regions of "linkage" where DNA variations appeared to be inherited along with the disease.
184 people, 65 of whom were affected with autism. They found a novel region -- a small section of the long arm of chromosome 12 -- that appeared to contain a gene that causes autism.
“ We have identified the smallest candidate region for a new autism gene, and with the highest statistical confidence, of any other study to date,” Haines said.
When the Duke study focused on families in which only males were affected, the evidence for linkage to this same region was enhanced significantly. The finding adds to the growing evidence that the causes of autism may be different between males and females, and suggests that this difference could stem from a gene that lies within this region of chromosome 12, Haines said.
According to the researchers, 19 genes are located within this candidate region. They are currently sequencing these candidate genes for genetic variations present in those individuals affected with the disease but not in their healthy relatives.
Genomes to Life Project - Proteomics
Identify the protein machines that carry out critical life functions and the gene regulatory networks that control these machines
The broader phenotype (autism)
Genetic pattern associated with the phenotype
The ‘broad’ phenotype?
How are genes a blueprint?
“ The DNA sequence (e.g., ATTCCGGA) . . . spells out the exact instructions required to create a particular organism with its own unique traits.”
A metaphor which describes cases in which there is a specific correspondence between genotype and phenotype
Blueprint-like modes of genetic transmission
Single gene or Mendellian
Specific genetic defects can be deadly or disabling
http://www.uaf.edu/psych/psyc240/exam1/index.html, Jim Allen , Ph.D
Phenylkitenuria, sickle cell, etc.
Sex-linked (23rd chromosome)
Traits are transmitted as separate units
Autosomes - 22 pairs
One pair from each parent
When 2 competing traits are inherited
Only 1 trait is expressed
Dominant-Recessive Inheritance Messinger
Traits are transmitted as separate units
25% risk of inheriting a “double-dose” of r genes
which may cause a serious birth defect
25% chance of inheriting two N ’s
thus being unaffected
50% chance of being a carrier as both parents are
23rd chromosomal pair
Male = XY (Missing an arm)
one Y branch not matched
so allele on corresponding X branch is expressed
Female = XX
each branch is matched
Male’s “x” inherited from mother
Women are carriers
Males represented disproportionately in sex linked disorders
baldness color-blindness, hemophilia
Baldness: maternal gf > f
Even sex-linked characteristics are dependent on environmental influences
Expression of baldness depends on circulating testosterone levels
Quantitative perspectives on gene*environment interface
The influence of genetic and environmental factors be distinguished and the influence of each can be quanitified using behavioral genetic methods (Plomin)
Measuring genetic and environmental influences on behavior
Finding genes for behaviors?
Twin Studies Messinger Monozygotic vs Dizygotic: human studies of genetic versus environment
Identical (MZ) twins share 100% of their genes
Fraternal (DZ) twins share 50% of their genes
Both types of twins have similar environments . . .
Greater behavioral similarity of identical twins indexes greater genetic influence
No genetic influence Messinger
Complete genetic influence Messinger
Genetic Influence on Human Psychological Traits: A Survey
“ There is now a large body of evidence that supports the conclusion that individual differences in most, if not all, reliably measured psychological traits, normal and abnormal, are substantively influenced by genetic factors.” (Bouchard, 2004)
Bouchard, T. J. (2004). "Genetic Influence on Human Psychological Traits: A Survey." Current Directions in Psychological Science 13 (4): 148-151.
Sources of Variance in Behavior
Gene x environment interaction
Estimates of genetic and environmental influence
Proportional in samples
Greater environmental variation
Will minimize genetic variation
Greater genetic variation
Will minimize environmental variation
E.g. Downs Syndrome
Why might adoption studies maximize estimates of genetic influence?
Can genetic effects increase with time?
Gene*Environment Interaction Messinger
Transactional perspective on gene*environment interface
“ It is not nature vs. nurture, but the interaction of nature and nurture that drives development.” Urie Bronfrenbrenner (what we just heard)
“ What will it take to make behavioral genetics truly developmental?”
In my opinion, the purely statistical population view will have to be abandoned in favor of the study of individuals:
An analysis of the bi-directional relations from gene action to the external environment over the life course, including the prenatal period.
Gottlieb, G. (2003). "." Human Development 46 (6): 337-355.
Previously modeled but not measured
Now parental monitoring, neighborhood deprivation account for small (2-5%) of environmental variation
What else should we be measuring?
Gene * Environment interactions
Development always involves this interaction
Specific statistical effects
Genetic effects on alcohol use are great in non-religious than religious households
Genetic effects on seeking specific environments –
Identical twins find similar friends
Identical twins treated more similarly (or differently) than fraternal twins?
Correlation or quasi-experimental designs; no causality
Intervention studies: prediction of treatment efficacy
Absence of psychopathology vs. competent functioning
Effects of genes
(Bakermans-Kranenburg, et al., 2008)
Relationship between breast feeding and IQ scores
(Caspi et al., 2007)
No single allele is risk-inducing under all contexts
(Belsky et al., 2007)
Putting genes in their environment
Each pair splits
Producing gamete with unique set of chromosomes
Gametes - sex cells
Fertilization of the ovum creates the zygote - New Cell
Disadvantages of the genes-as-blueprint metaphor
Genes are bits of protein in a primarily liquid nucleus in a primarily liquid cell surrounded by other cells in a primarily liquid uterine environment
Without an “environment,” genes are bits of protein
From a lump of jelly to an organism
How do genes actually work?
Prenatal development is usually divided into three main periods.
covers the first two weeks after conception
ends when the zygote implants into the wall of the mother's uterus.
from two to eight weeks following conception
the major organs and bodily systems form
from eight weeks after conception until birth
grows tremendously in size and weight.
Zygotic cell differentiation Messinger
From zygote to embryo Messinger
The zygote grows through cell division
Mitosis - One for one copying of all 23 chromosomes
All cells contain the same genetic information in their nuclei
But qualitatively different types of cells develop in different parts of the body
How does this occur?
General processes yield specific outcomes
Cells clump together as a sphere
This changes the extra-cellular environment of cells on the inside and outside of the sphere
Differences in environment impact cell’s genetic make-up to activate different proteins
Genes in Environment
Environmental factors influence development from the start
Cells are environments
The uterus is an environment
The fetus participates in actively constructing its own development
it is not passively constructed
Creation of a tube Messinger
Cells groups in which specific molecular processes occur with boundaries with other groups
Regulator genes activate and de-activate other genes within these groups
Cells impact each other such that a nerve cell transplanted to the liver region becomes a liver cell after several replications
What do you think?
Stem cell debate
Assistive reproduction technology
Plomin, et al. The genetic basis of complex human behaviors.
Plomin, R., & Rutter, M. (1998). Child development, molecular genetics, and what to do with genes once they are found. Child Development, 69 (4), 1223-1242.
Rutter. M. (in press . Nature, nurture, and development: From evangelism through science towards policy and practice. Child Development .
Collins , W. A., Maccoby, E. E., Steinberg, L., Hetherington, E. M., & Bornstein, M. H. (2000). Contemporary research on parenting: The case for nature and nurture. American Psychologist, 55(2), 218-232.
Sleigh, M. J., Columbus, R. F., & Lickliter, R. (1998). Intersensory experience and early perceptual development: Postnatal experience with multimodal maternal cues affects intersensory responsiveness in Bobwhite Quail Chicks. Developmental Psychology, 34 (2), 215-223.