Nature vs nutureHow much of what we become is genetically determined and how much is environmental ?

Learning Outcomes

• By the end of the session you will be able to:• Understand the nature of genetics and their

influence on development• Be aware of the connection between genetics,

health and pre- disposition to illness

• The view that humans acquire all or almost all their behavioural traits from "nurture" was termed tabula rasa ("blank slate") by philosopher John Locke, and proposes that humans develop only from environmental influences.

The history of genetics • Inheritance 1880

• Human genome 2003• Genotypes• Phenotypes

James D. Watson and Francis Crick determined the structure of DNA in 1953, using the X-ray crystallography work of Rosalind Franklin and Maurice Wilkins that indicated DNA had a helical structure (i.e., shaped like a corkscrew)

• genetic disorder library - Utah University

• http://learn.genetics.utah.edu/content/begin/traits/predictdisorder/

Genetic mutation

Agents that damage DNA• Radiation• Chemicals in the

environment• Drugs• viruses

Types of DNA Damage• Deamination• Mismatches• Breaks and crosslinks

Heritability

• Heritability is a concept that summarises how much of the variation in a trait is due to variation in genetic factors.

• In many cases, it has been found that genes make a substantial contribution, including psychological traits such as intelligence and personality.

• Yet heritability may differ in other circumstances, for instance environmental deprivation

• Examples of low, medium, and high heritability traits include:• High heritability Medium heritability Low heritability

• Blood type Weight Specific language• Eye colour Religiosity Specific

religion

Heritability

• does it depend on other variables ?

• Davis, O.S.P, Haworth, C.M.A., Lewis, C.M., & Plomin, R. (2012). Visual analysis of geocoded twin data puts nature and nurture on the map. Molecular Psychiatry, 17, 867-874 DOI: 10.1038/mp.2012.68

The ethical dilemmas of this information ?The Human Genome project

• It is 2010, and Joe Schmoe has been charged with assault. The physical evidence supporting his guilt is overwhelming and he pleads guilty. In preparation for his sentencing hearing, Joe's lawyer asks him to undergo genetic tests to determine whether he carries any of four genetic mutations that have been associated with violent behaviour. The tests, while controversial, show that Joe's DNA does, in fact, contain all four mutations. Based on these results, Joe's lawyer will argue that Joe should be sent to a psychiatric facility rather than to state prison. He claims that because Joe's genetic status predisposed him to this violent act, it would be unfair to sentence him as a criminal for behaviour over which he had essentially no control.

• Questions:• If you were the judge at Joe's sentencing hearing, how, if at all, would the results of this

controversial genetic test influence your decision?• How would your decision be influenced if Joe had only 1 of the 4 mutations associated with violent

behavior?• What would be your decision if Joe was shown to suffer from a mental illness such as

schizophrenia? How come?• If Joe gets sent to prison and tries to get released on parole fifteen years later, should the fact that

he may have a genetic predisposition to violent behavior be used to keep him in prison, even if his behaviour has been consistently good during his incarceration?

• In the future, should all newborn babies be screened to determine if they have genetic mutations that could be linked to violent behaviour? How come?

Further debates•This is a complex debate because so much is still unknown• There are also many sub divisions to this debate• On the nature side; what is genetically inherited

from birth and what is genetically determined following environmental exposure ?

• On the nurture side there is the structure versus agency debate i.e. socialisation versus individual autonomy. – Is the evidence produced by studies in the last century which demonstrate the

mother and family as highly influential mediators of nurture less relevant today when we are wildly exposed to other’s from an early age The Nurture Assumption, author Judith Harris