GENETICS:Adoption Studies, Twin Studies, Sequential Design, Follow back studies

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Abnormal Psychology PSY404

LESSON 9

GENETICS

Genetics means what we inherit from our parents. I got my mother's eyes, I got hair like my father, and I

am stubborn like my father. This suggests how we look, feel and behave is predetermined by our genetic

make up. The field of behavior genetics deals with phenomenon how genetic information in form of

chromosomes from both father and mother is transmitted to children.

Chromosomes contain genes; the genes transmit a biochemical code which is responsible for determining

the structure and activity of the body's protein. At the biochemical level, the genetic code leads to

physiological and physical differences. These differences include like height, weight, color of hair and color

of eyes, which are the result of number of different genes. Genetic research is growing rapidly because

people are interested to know the gender of their unborn child and the intelligence level of their children.

Table 1

Terms used in genetic research

Term

Definition

The genetic characteristics a person inherits e.g.

someone may inherit a genetic pre-disposition

Genotype

for a disorder but the genotype may or may not

result in the disorder.

A person observed behavior and trait patterns. A

Phenotype

disorder may be inherited but it is the phenotype

expression of the genotype that is seen.

A gene whose heredity characteristics prevail in

Dominant Gene

the offspring.

A gene whose heredity characteristics are seen

Recessive Gene

only when paired with another identical gene.

Single dominant A single gene whose expression prevails in the

gene

offspring (for example, colorblindness).

Several genes whose expression prevails in the

Multiple genes

offspring (for example, height)

A portion of a gene; DNA stands for

DNA fragment

deoxyribonucleic acid, the principal component

of genes.

Some important terms used in behavior genetics are following

Phenotype refers to observable characteristics or behavior of the individual whereas genotype refers to

unique genetic make up of individual.

Dominant gene is one which is expressed in offspring. If the offspring has dark black hair then dominant

genes for hair color is black.

Recessive gene is one which is expressed when paired with an identical one.

Single dominant gene is one which is expressed as a rare types of disorder such colorblindness.

Multiple genes refer to trait that is expressed in the offspring due to a number of genes such as height.

DNA stands for deoxyribonucleic acid, the principal component of genes.

Example

A person with Down syndrome typically has mental retardation, a variety of other physical characteristics

such as slanted eyes and thick tongue. These characteristics are the phenotype. The genotype is the extra

Abnormal Psychology PSY404

21st chromosome that causes Down syndrome. We have following traditional research strategies which

scientists use as they study interaction between environment and genetics.

Table 2

Methods, Goals and Limitations of Genetics Research

Method

Question to be answered

Limitations

Cannot

separate

genetic

and

Family Study

Does the disorder runs in families?

environmental effects

Cannot

separate

genetic

and

environmental effects, although it can

What factor influence development of

High Risk Study

characterize the impact of specific

the disorder?

effects; results generalizable only to

similar high-risk populations.

Rare examples; environmental\ factors

Twin Study

Is the disorder inherited?

uncontrolled

Difficult to get accurate information on

Can we separate genetic and

Adoption Study

biological parents or to control

environmental contributions?

confounding factors.

Pedigree

Requires large inbred families with the

What is the nature of inheritance?

Analysis

disorder

Linkage

Best with disorders controlled by a

Where is the gene located

Analysis

single dominant gene.

Family Studies (whether a disorder runs in family?)

These studies verify whether the frequency or prevalence of a particular disorder is higher among the family

members, then in the general population.

1- The investigator first identifies a patient's with a particular disorder and a comparison group without the

disorder.

2-The next step is to obtain information about each close relative of the participants both with and without

the disorder either by directly interviewing them or, if that is not possible, by asking each participant or

someone else in the family about the relatives.

3-Finally, the researcher compares the rates of the disorder to see if these rates are higher among the

relatives of patients with the disorder than in the control group representing the general population.

In family studies, scientists examine a behavioral pattern in the context of family.

If there is a genetic influence, the trait should occur in the first degree relatives (parents, siblings and

offspring) then in the second degree or distant relatives. The presence of a trait in distant relatives in terms

should be somewhat greater then in the population as a whole.

Example

William Grove at University of the Minnesota, who used the family study method to study schizophrenia.

He administered structured interviews, questionnaires and tasks to seventeen schizophrenic patients,

sixty one first degree relatives and eighteen normal control subjects. The result showed that schizophrenic

and their relatives scored significantly more in the abnormal direction, then the normal control subjects.

High Risk Method

This is a type of family study in which the child of a parent with an identified disorder is studied. In other

words by comparing development and eventual outcome of a child of a disordered parent with a child of

normal parents, the researchers hopes to learn about the child at risk for developing a disorder. These

studies have shown that a child of a depressed mother is more likely then a child of a non-depressive

mother

to be depressed

ii.

to experience conflict with mother.

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Adoption Studies

How we can separate the influence of environment from genetic influences in families? One way is through

adoption studies. Scientists identify adoptee, which has a particular pattern or psychological disorder and

they attempt to locate first degree relatives who were raised in different family setups.

Example:

Suppose a young man has a disorder and he discovers that his brother was adopted as baby and brought up

in a different home. They study whether siblings brought up in different families display the disorder to the

same extent as the original subject. If brothers are raised in different families have the disorders more

frequently then would be expected by chance. Then we can conclude that genetic inheritance is a

contributor.

In adoption study, cross fostering is a type where researcher study, children of normal biological parents

or disordered parents.

Another type of adoption studies is the family study of adoptee, where children adopted by people are

studied.

Twin Studies

If we want to study genes closely, we should study the development of identical twins (monozygotic twins).

The twins who do not look alike but have identical genes are called fraternal twins (dizygotic twins). In twin

studies, researchers want to know whether identical twins have the same traits or different.

Plomin in 1990, points out correlation for height in identical twins as 0.90 and in fraternal as 0.45. These

findings show height is 90 percent heritable trait.

Michael Lyons and his colleagues in 1995 conducted a study on anti-social behavior among the members of

Vietnam era twin registry. All the subjects were twins. The researchers concluded that family environment

was a strong influence in inheriting anti-social trait in another words, after the individual grew up and left

his family early environmental influences mattered less and less and it was genes only.

Genetic linkage and association studies

The results of series of family, twins and adoption studies suggest that a particular disorder has a genetic

component but to locate that defected gene or genes is difficult. To locate a defected gene, there are two

methods Genetic Linkage and Association Studies.

The basic principle of genetic linkage analysis is simple. When a family disorder is studied, other inherited

characteristics are also measured at the same time. These other characteristics are called genetic markers.

The genes for a disorder and the genetic marker lays close together on the same chromosome e.g. in

studying bipolar affective disorder, researchers found two genetic markers on chromosome 11, suggesting

that a gene for bipolar affective disorder might be on chromosome 11. This is genetic linkage study.

The second strategy for locating specific genes is called association studies. It also uses genetic markers. In

association studies, researchers compare people with and people without the disorder. If certain genetic

markers occur more often people with the disorder, it is assumed that the genetic markers are close to the

genes involved with the disorder. Association studies are better able to identify genes that may only weekly

be associated with a disorder.

To Study Behavior Across Time

When we want to know whether a behavior pattern changes or remains the same over time, we use cross

sectional designs or longitudinal designs. Researcher wants to inquire

What course does a disorder follow?

What role genetics play in this disorder?

Are the affects of the treatment meaningful?

so we want to inquire about the study of psychopathology across time.

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Longitudinal designs (same people followed across time)

One way to examine what course a disorder follows is through longitudinal designs. In longitudinal study

we study changes in behavior over time by repeatedly measuring the same subjects or participants at

selected intervals of time.

This allows the researcher to assess individual behavior change.

Example

We may study depression in women earthquake survivors in the year 2006 then in the year 2007.

M. Seligman (1992) conducted a longitudinal study on depression among children.

The sample was 508 third grade children who were interviewed every 6 month over a period of 5- year. The

depression symptoms included sadness, trouble in the patterns of sleeping and eating.

The longitudinal research is costly and time consuming.

Cross Sectional Studies (people of different ages viewed at the same time)

In cross sectional studies, we examine the same behavioral characteristics in different individuals at different

ages at the same time e.g. we might study the symptoms of a disorder assessed at one particular time in

children, adolescents and adults.

EXAMPLE

We study depression symptoms among women earthquake survivors who are 30years, 50years and 60years

in the year 2006.

Sequential Design

The combination of longitudinal and cross sectional designs in a strategy is called Sequential Design.

Julia Wallace and Micheal O'Hara (1992) used both, longitudinal and cross sectional design explored

whether depression among 65 year olds and above, change over time.

The cross sectional design included interviewing the different age ranges like 65-69, 70-74, 75-79, 80-84, 85-

89,and 90- above. The longitudinal design included interviewing the subjects 3 and 6 years later. Both parts

of the sequential design produced the same findings that is depression seem to increase as we grow old but

social support can prevent it.

Follow up studies

In follow up studies, we identify patients at a particular point, such as when they are first diagnosed and

study these people again at a later time (in future).

Follow back studies

Follow back studies where earlier records at school or treatment agencies are examined.

High risks studies

Where researchers look at children, exposed to conditions that are thought to contribute to disorder such as

a child living with a depressed mother, or children living in poverty or children in war zone areas,

in both of these types of studies, cross sectional and longitudinal, we study psychopathology across time.

Studying Behavior across Cultures

We study people from different cultures but unfortunately most research literature is available about

western culture only. In Malaysia, researchers have described a disorder, they called Gila which has some

features of schizophrenia but it differs from it in important ways.

The independent variable is the effect of culture on behavior so we can say that the difference between

looking at culture as a treatment and our typical design is important. People in different cultures see the

same behaviors very differently and researchers have trouble in comparing the incidents and the prevalence

rates.

Example

Depression is one disorder seen differently in different cultures.

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The Power of a Program of Research

When we examine different research methods independently, it is important to understand that we are

asking a type of question or we are conducting research using a strategy or a method. So actually we are

asking or inquiring about the power of the program of research.

It was Patterson and his colleagues at university of Oregon studied the aggressive behavior of children.

They wanted to know why children are aggressive.

Patterson also looked at prevalence of aggressiveness of children and the prevalence rate was 25%. In other

words some levels of aggression appear to be normal. But when that normal level of aggression exceedes, it

become pathological.

Patterson also conducted experimental studies in which, he observed how a five year old boy reacted to his

mother's attempt to change his problem behavior. The boy's mother restrained the child but did not talk to

him during this time. Later, in the experimental condition, the mother talked to the son in a positive way

when he complained. It was found that the boy was more likely to complain about being restrained then

when he was talked with. Patterson concluded that the role of mother is influential in modifying son's

behavior. As this example indicates, research is conducted in stages or phases and a complete picture of any

behavior can be seen only after looking at it from many different perspectives.

Replication

The real strength of a research program lies in its ability to replicate its findings in different ways to built

confidence in the results. If you look back at the research strategies we have described, you will find that

replication is one of the most important aspects of each research method. The more time a researcher

repeats a process (about the behavior he is studying or changes he is expecting). The more sure he is about

what cause the changes.

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