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
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 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
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
i.
to be depressed
ii.
to experience conflict with mother.
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.
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, 7579, 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.
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.