Biological theories- genetic

Who is the theorist of the XYY theory,

Jacob et al

What is the XYY theory

This theory of criminality suggests that some crime may be attributable to a chromosomal abnormality.

Number of chromosomes

Structured in cell nuclei, carries our genes, humans usually have 46.

Chromosomal abnormalities

Involves the presence of an extra chromosome. XYY

XY, XX and XYY

XX in women, XY in men, XYY aggressive behaviour

What did Jacob et al do

Suggested that men with XYY chromosome were more aggressive than a normal XY man.

Features of a XYY person

Above average height, large head and teeth, borderline intelligence

Behavioural characteristics of ab XYY person

More aggressive and violent than other men

How does the XYY theory link to criminality

Due to these characteristics, XYY males are more likely to commit crimes.

Examples of the XYY theory.

There are not criminals proven to have XYY.

Name three strengths’s of the XYY theory

Jacob et al found that a number of men in prison had XYY chromosomes.

Gesh et al demonstrates that diet

can positively affect aggressive

behaviour

Adler et al indicated that it is possible that aggression and violent behaviour is partly determined by genetic factors.

This theory also promoted a

scientific approach

Same three weaknesses of the XYY theory

Their studies focus mainly on males and

so it does not explain criminality within

females.

Theigaard researched the traits of XYY

men compared to XY men abd found that

aggression was not associated with the

XYY men

Many early studies of this theory was studied in prisons and so does not represent the whole population.

Who is the theorist behind the Twin studies

Lange

What is the twin studies

The Twin studies supports the contention that a heritable trait may increase risk for criminal behaviour.

What are the two types of twins

Monozygotic, identical.

What % of DNA do the two types of twins share

Monozygotic, 100% of DNA while Dizygotic share 50% of DNA

What is concordance

Similar beliefs, behaviours and personalities which people share

What is concordance rates

Likelihood that both individuals will display the same traits

How does the Twin studies link to criminality

Due to shared DNA and concordance rates, suggests that crime is genetically based

Name two case examples for the twin studies

Kray and Whitehead twins

Name three strengths of the Twin studies

The results of this theory have

helped in the prevention of

vulnerable diseases.

This theory avoids unethical

manipulation of the humans genes

or environment

This theory also has case examples

to support their ideas such as the

Kray and whitehead twins

Name three limitations of the Twin studies

The theorists had only used a small

sample group and so it may not represent

the general population

Within the early studies of this theory,

this theory lacked control and validity as

to whether the twins were DZ or MZ.

This theory also does not explain

criminality amongst people who are not

twins.

Who is the theorist behind the adoption studies

Mednic et al

What does the adoption study suggest

Explaining that criminal behaviour is the comparison of criminal’s both with their biological and adoptive parents

What are adoptive parents

Individuals who legally adopts a child which is not biologically their own.

What are biological parents

Genetic mother and father of a child

How dos the term heritable link to the adoption studies

Crime can be inherited from biological parents

How does the term aggression link to the adoption studies

Aggression can be inherited

What studies did Medick et al conduct

14,000 adoptive children in Denmark. Highest rates of criminal convictions occurred in both biological and adoptive children who had criminal parents

How does the adoption studies link to criminality

Some extent criminality is genetic but also environmental

Name two case examples of the adoption studies

David Berkowitz and Ted Bundy

Name three strengths of the adoption studies

Has case studies such ad David Berkowitz and Ted Bundy

These findings can help early interventions with children at risk of becoming criminal

Separates the effects of genetics from their upbringing

Name three limitations of the adoption theory

Information about biological parents are not always available

Raises ethical concerns including privacy

There is potential for bias as adoptive parents are often screened which may affect results