1.)
What is a “Twin Study”?
2.)
Why do scientists and psychologists study twins?
Twin studies are normally conducted
to further support or reject biological influences on a life forms development
in many areas, such as mental illness, intelligence, and behavior. It states
that that if the concordance rate is higher on twin study when compared to a
non-twin study, the results can suggest that there is a biological link in the
area they are researching, and this is mainly due to twins sharing the same
genes.
3.) What, in general, has been learned from past studies?
With their similar genetic makeup, twins represent an ideal
opportunity to study health and behavior issues. From twin studies, it
is possible to determine how genetic and environmental factors influence
health. Studies can also provide scientific insights into twins and
genetics, including conditions such as diabetes, heart disease, and
obesity, as well as the effects of alcohol and tobacco use. By
identifying the genetic components of these health problems and others
through twins research, it is possible to develop early interventions
and treatments.
For the National Institutes of Health and other clients, researchers at SRI's Center for Health Sciences conduct twins research studies on the pharmacokinetics of nicotine, the metabolism of commonly used medications, genetic susceptibility to cancer-causing chemicals, and sleep patterns in young twins.
The continually growing and diverse Twin Research Registry at SRI International includes more than 3,000 members who volunteer to participate in SRI twin research studies.
For the National Institutes of Health and other clients, researchers at SRI's Center for Health Sciences conduct twins research studies on the pharmacokinetics of nicotine, the metabolism of commonly used medications, genetic susceptibility to cancer-causing chemicals, and sleep patterns in young twins.
The continually growing and diverse Twin Research Registry at SRI International includes more than 3,000 members who volunteer to participate in SRI twin research studies.
Twin Facts and Figures
Fascination with twins is part of every culture -- and dates back centuries. Some interesting twin "facts and figures" include:-
In ancient times, doubleness in nature was often interpreted as a
manifestation of the supernatural or intervention by the gods -- that is
why many gods in different religions are twins or supertwins.
-
In the Aztecs, Babylonian, Zuni and Ashanti cultural myths, twins
took the form of warriors, builders, healers, symbols of light, water or
thunder.
-
Native American tribes in the Northwest believed that twins were actually salmon in human disguise.
-
The frequency of twin births reported vary from country to country and range from 1 in 80 to 1 in 140.
-
When it comes to phobias -- like fear of heights, of closed spaces,
or of open spaces -- twins often respond similarly. Twins often share
phobias, and more often than not if one twin harbors an irrational fear,
the other does too.
4.) What are the differences between a Monozygotic and dizygotic twin?
Twin can either be monozygotic meaning that they develop from one zygote that splits and forms two embryos or dizygotic, which develop from two separate eggs that are fertilized by two separate sperms. This difference in fertilization in dizygotic shares an average of 50% of their genetic material and the monozygotic shares 100% of their genetic material. This difference in amount of shared genetic material sets the stage for a marvelous natural experiment and it is the basis of the twin method for research.
5.) What is and "adoption study"?
An "adoption study," is is one form of a clinical genetic study designed to evaluate genetic and environmental influences on phenotype The study provides a unique opportunity to examine gene and gene by environment interactions for a variety of behavioral, psychiatric and medical disorders.
Adoption studies provide a unique research model where biological genetic effects can be estimated. Adoption studies can be helpful in uncovering gene–environment interactions in complex behavioral and psychiatric disorders. Adoption
genetic studies utilize a variety of statistical techniques including
calculation of odds ratios, logistic regression, log-linear statistical
monitoring and path analysis.Recent
advances in adoption study research have occurred by combining
molecular genetic techniques to the genetic and environmental data of
adoptees. Increased
privacy concerns and privacy laws related to biological parent
anonymity have made adoption studies more difficult to design and
implement.
An "adoption study," is is one form of a clinical genetic study designed to evaluate genetic and environmental influences on phenotype The study provides a unique opportunity to examine gene and gene by environment interactions for a variety of behavioral, psychiatric and medical disorders.
Adoption studies provide a unique research model where biological genetic effects can be estimated. Adoption studies can be helpful in uncovering gene–environment interactions in complex behavioral and psychiatric disorders. Adoption
genetic studies utilize a variety of statistical techniques including
calculation of odds ratios, logistic regression, log-linear statistical
monitoring and path analysis.Recent
advances in adoption study research have occurred by combining
molecular genetic techniques to the genetic and environmental data of
adoptees. Increased
privacy concerns and privacy laws related to biological parent
anonymity have made adoption studies more difficult to design and
implement.
6.) How do adoption studies help researchers understand the question of how human traits are influenced by either genetic or environmental influences?
Adoption studies have shown the strong influence of genes (or nature). For instance, the Texas Adoption Project found "little similarity between adopted children and their siblings and greater similarity between adopted children and their biological parents."
Adoption studies have shown the strong influence of genes (or nature). For instance, the Texas Adoption Project found "little similarity between adopted children and their siblings and greater similarity between adopted children and their biological parents."
7.) Describe the Minnesota Study of Twins Reared Apart (MISTRA)
The Minnesota Study of Twins Reared Apart (MISTRA) was one of the most important psychological studies of the last 50 years. It began in 1979, at a time when it was widely believed that intelligence and personality were almost infinitely malleable by the environment. By the time the study ended 20 years later, it had played a key role in overthrowing this dogma. It established beyond any doubt that genes are crucial to who we are.
http://web.missouri.edu/~segerti/1000H/Bouchard.pdf
http://www.amren.com/features/2012/07/science-versus-ideology/
The Minnesota Study of Twins Reared Apart (MISTRA) was one of the most important psychological studies of the last 50 years. It began in 1979, at a time when it was widely believed that intelligence and personality were almost infinitely malleable by the environment. By the time the study ended 20 years later, it had played a key role in overthrowing this dogma. It established beyond any doubt that genes are crucial to who we are.
http://web.missouri.edu/~segerti/1000H/Bouchard.pdf
http://www.amren.com/features/2012/07/science-versus-ideology/
8.) Identify the findings from the MISTRA.
MISTRA yielded what amount to two different kinds of findings: quantitative and impressionistic. The former come from personality, intelligence, medical, and other testing, whereas the latter include the almost eerie, unmeasurable ways in which MZA twins are alike.
The first twin pair MISTRA evaluated was particularly striking. The two men met when they were 39, and found that both had been in law enforcement but were now working as firemen. Both had loved math in school and hated spelling. Both did woodworking as a hobby, and their favorite vacation spot was Pas Grille Beach in Florida. One had named his son James Alan and the other had named his James Allan. They looked very much alike, had the same smoking habits, and always held a beer can with a pinky under the can. Both had put on 10 pounds at the same age for no apparent reason.
Not all twins were so alike, but this book is full of astonishing similarities. In one MZA pair, one twin was reared in Germany and the other in Trinidad, and they had never met before they came to Minnesota for testing. When they arrived at the airport each was wearing a light blue shirt with epaulettes, and wire-rimmed glasses. They both collected rubber bands, which they wore around their wrists, and washed their hands both before and after using the bathroom. Both liked to startle people by sneezing loudly in elevators.
One pair of MZA women both wet the bed until age 12 or 13. When they were teenagers they started having nightmares about the same things: fishhooks and doorknobs. Both had problems with nightmares for more than ten years.
One pair of MZA men had been overweight until middle school and then became quite thin. They had speech problems for which they received therapy in kindergarten or grade school. Both were diagnosed as hyperactive at about the same age, and both were actively and openly homosexual.
A pair of female MZA twins from Australia found each other because of a case of mistaken identity. They both worked as fashion buyers for competing department stores, and a customer accused one of moonlight for the competition. They were both very elegant, dressed with the same style and the same kind of jewelry, smoked the same cigarettes, and had the same hairstyle, posture, tastes, and speaking voice. One MZA pair of male twins were both fitness fanatics who ran their own body-building gyms. MZA twins generally have the same posture and arrange their hands and legs in the same way while DT twins do not.
MISTRA yielded what amount to two different kinds of findings: quantitative and impressionistic. The former come from personality, intelligence, medical, and other testing, whereas the latter include the almost eerie, unmeasurable ways in which MZA twins are alike.
The first twin pair MISTRA evaluated was particularly striking. The two men met when they were 39, and found that both had been in law enforcement but were now working as firemen. Both had loved math in school and hated spelling. Both did woodworking as a hobby, and their favorite vacation spot was Pas Grille Beach in Florida. One had named his son James Alan and the other had named his James Allan. They looked very much alike, had the same smoking habits, and always held a beer can with a pinky under the can. Both had put on 10 pounds at the same age for no apparent reason.
Not all twins were so alike, but this book is full of astonishing similarities. In one MZA pair, one twin was reared in Germany and the other in Trinidad, and they had never met before they came to Minnesota for testing. When they arrived at the airport each was wearing a light blue shirt with epaulettes, and wire-rimmed glasses. They both collected rubber bands, which they wore around their wrists, and washed their hands both before and after using the bathroom. Both liked to startle people by sneezing loudly in elevators.
One pair of MZA women both wet the bed until age 12 or 13. When they were teenagers they started having nightmares about the same things: fishhooks and doorknobs. Both had problems with nightmares for more than ten years.
One pair of MZA men had been overweight until middle school and then became quite thin. They had speech problems for which they received therapy in kindergarten or grade school. Both were diagnosed as hyperactive at about the same age, and both were actively and openly homosexual.
A pair of female MZA twins from Australia found each other because of a case of mistaken identity. They both worked as fashion buyers for competing department stores, and a customer accused one of moonlight for the competition. They were both very elegant, dressed with the same style and the same kind of jewelry, smoked the same cigarettes, and had the same hairstyle, posture, tastes, and speaking voice. One MZA pair of male twins were both fitness fanatics who ran their own body-building gyms. MZA twins generally have the same posture and arrange their hands and legs in the same way while DT twins do not.
9.) What are the limitations of twin and adoption studies?
In Twin studies, Monozygotic twins are rarely separated at birth and raised in a totally different environment, and are reared together sharing many of the same experiences. Dizygotic twins reared together may not share the same experiences due to levels of attractiveness or temperament.
On the other hand,selective placement is a problem tending babies to be placed with families similar in background to the natural parents, adopted children as well as twins are not representative of the children, and the act of being given up for adoption may affect the child's behavior.
10.) What are the ethical associated with twin and adoption studies?
- Unlike twin studies, in adoption studies individuals are exposed to a different environment to their biological or genetic relatives. This makes it easier to separate genetic and environmental factors.
- These studies are not easy to undertake as information on an adoptee and their biological families may not be available.
- There are ethical issues to be considered when approaching members of the biological family, about a child who was adopted many years ago.
- Adoption is not a random process, meaning that children are often placed in families resembling their biological family or in families that have been specially selected for other reasons.
- Adoption is also an unusual event in itself, leading to a small sample size.
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