Twins and Genetics Behavioral genetics is a field of research that investigates the relative effects of heredity and environment on behavior and ability (Plomin, 1997). Two of the primary methods used by behavioral geneticists are the twin study method, first used by Galton (1975) in his studies of heredity, and the adoption method. In the twin study method, researchers studies identical twins (monozygotic twins) and fraternal twins (dizygotic twins) to determine how much they resemble each other on a variety of characteristics. Identical twins have exactly the same genes because a single sperm cell of the father fertilizers a single egg of the mother, forming a cell that then splits and forms two human beings-"carbon copies." But fraternal twins are no more alike genetically than any two siblings born in the same parents. In the case of fraternal twins, two separate sperm cells fertilize two separate eggs that happen to be released at the same time during ovulation. Twins, who are raised together, whether identical or fraternal, have similar environments. If identical twins raised together are found to be more alike than fraternal twins on a certain trait, then that trait is assumed to be more influenced by heredity. But if identical twins and fraternal twins from similar environments do not differ on a trait, then that trait is assumed to be influenced more by environment. In the adopting method, behavioral geneticists study children adopted shortly after birth. By comparing their abilities and personality traits to those o their adoptive family members with whom they live and those of their biological parents whom they may have met, researchers can disentangle the effect of heredity and environment (Plomin et al., 19... ... middle of paper ... ...dy of twins reared apart. Science, 250, 223-228. Bouchard, Tomas (1994). Genes, environment, and personality. Science, 164, 329-334. Finkel, D. (1995). Heritability of cognitive abilities in adult twins: Comparison of Minnesota and Swedish data. Behavior Genetics, 25, 421-432. Galton, F. (1975). The history of twins as a criterion of the relative powers of nature and nurture. Journal of the Royal Anthropological institute, 5, 391-406. [8] Holden, Constance. (1980). Identical twins reared apart. Science, 207, 1324-1328. Lykken, D.T (1992). Emergenesis: genetics traits that may not run in famioies. American Psychologist, 47, 1496- 1502. Plomin, Robert. (1997). Molecular genetics and psychology. Current Directions in Psychology Science, 4, 114-117. Plomin, Robert. (1988). Enviorment aznd genes: Determinants of behavior. American Psychology, 44, 105-111. [8,13]
Twins are truly fascinating from the time of separation of the embryo to birth; and still the complexity of twinning is not yet fully understood among the scientific world. Scientists have studied the human body from the time of prenatal development to birth, and still are in awe of the formation of twins. Research in twinning is ever more increasing in this field, leadi...
Identical, conjoined, and half-twins are all examples of intrinsic variability in humans. Intrinsic variability exists in all animals and is an adaptive mechanism built into the nervous system in response to input. This mechanism allows humans to distinguish the same inputs as different from one another and therefore, the possible outputs vary with time. It is possible that due to identical genetic input, the twins could share identical neural pathways and identical I-Functions. This hypothesis could explain the identical behaviors and inter-connectedness of feelings and thoughts that twins share. Differences that are seen in twin behaviors could simply be due to intrinsic variability causing differing output or behaviors.
A complex and relatively new field of study, behavioral genetics is particularly interesting because is sheds light on the inner workings of a favorite subject: ourselves. Human behavioral genetics is broadly defined as the examination and characterization of genes as a basis for human behavior. The link between genetics and behavior was first recognized by Sir Francis Galton, a 19th century scientist and cousin of the very famous Charles Darwin, who studied the heritability of mental abilities of close relatives and family members (Stigler, 2010). Since then, genetics has been linked to many more behavioral phenotypes from eating and mating activities to substance abuse, social attitudes, violence and mental abilities. Geneticists are able to study this by analyzing parallels in physical and behavioral characteristics of families and populations (Rothstein, 2005). However, as with many other new scientific fields, the study of behavioral genetics and its implications has been the subject of increasing scrutiny and co...
12)De Waal, Frans B.M. (1999). The end of nature versus nurture. Scientific American, 281(6), 94-99. Retrieved from Expanded Academic.
Steen, R. Grant. DNA and Destiny: Nurture and Nature in Human Behavior. New York: Plenum Press, 1996.
People are often curious as to how something that seems as complicated as conjoined twins can occur, yet, it is a fairly simple process. There are basically two different ways which they can be formed. The first one includes the embryo splitting, and then stopping after a certain amount of time, usually 13-15 days after conception. The other way that scientists have discovered which allows conjoined twins to be formed is by separate embryos fusing together. The embryo splits off into two separate embryos and each begins to form on its own. Several days after conception, the separate embryos will then fuse themselves back together, causing the twins to be conjoined. It is not genetically clear why these mutations occur; however, it is clear that everything happens for a reason.
The nature- nurture debate has many different case studies, which often questions environmental and hereditary aspects of the nature- nurture debate. A tangent which is focused on in this essay is how the case studies of schizophrenia and IQ, specifically affect twin and adoption studies. This essay will firstly, give a brief outline of the nature-nurture debate and the definitions of twin and adoption studies. Secondly, it will illustrate two main case studies, which are IQ and Schizophrenia studies. Thirdly, will contrast and compare the two and research’s impact on the case studies in regards to nature vs. nurture and finally, will conclude with the impact of the nature-nurture debate and twin and adoption studies.
In a study done on the genetic and environmental factors influencing the emergence of these traits it was shown that both of these play large factors. The researchers studied one hundred and twenty-three pairs of identical twins and one hundred and twenty-seven pairs of fraternal
Over the last couple of decades scientist, psychologist, and people have questioned over the idea, and the stereo typical question of nature versus nurture. Using twin studies, scientist have been given the understanding that the environment and heredity influence their behavior development. With using the adoption in twin studies, the doctors and scientists have been able to tell the extent to which the resemblance and families is due to the jeans that are shared and due to the environment that is shared. Because of the jeans that are identical carried by the monozygotic twins, identical twins, there has been a great appeal to most scientists and doctors. Psychologist have been able to link the strong genetic
In the textbook, Personality Psychology, this is the first case presented (in chapter 6) is of twins separated at birth and then raised with two different families, still showed very striking similarities throughout their lives. Such as marrying women with the same names and also liking the same type of cigarettes, beer and profession. Identical twins are the most identical due to having the same genetic make up, so if they are showing similar likes and dislikes it leads me to believe that we may have some aspect of a predetermined set of traits that are then incorporated into our
They also look at Genetic Epidemiological Studies. These three studies deal with twins in relation to th...
I have always been fascinated by conjoined twins and have always had questions about them like; what do the Siamese have to do with conjoined twins? Why does this form of twin happen? What, if any genes cause this? What types of Conjoined twins are there? How does the environment affect, if at all, the biological families' gene pool? In my research in efforts to prepare this paper, I found the answers to this question and many more. This term paper will cover the types of conjoined twins, the biological occurrence that causes conjoined twins, a look into some of the genetic and environmental causes of conjoined twins, the types of conjoined twins and the genetic and social impact of conjoined twins.
Sir Francis Galton, father of eugenics, was an English Victorian polymath. He specialized in psychology, anthropology and is most well-known for his work on Eugenics. His intrigue into genetic variation in the human population was sparked by his cousin’s publication of “The Origin of Species” in 1859. Gal...
Beckwith, J. (2002). Geneticists in society, society in genetics. In J. Alper (Ed.), The double-edged helix (pp. 39-57). Baltimore: The Johns Hopkins University Press.
The nature versus nurture debate has lasted centuries due to the difficulty of separating genetic and environmental factors in humans. Studies on behavioral genetics measure similarity between subjects, but cannot locate its origin. For this, a control must be present, leading scientists to twin research. Identical twins have the exact same DNA, differing from fraternal twins with only 50% similarity, no greater than average siblings. Identical twins offer a natural experiment that allows researchers to separate the influence of genes from experience (Segal 87). A famous study conducted by the University of Minnesota reunited Jim Springer and Jim Lewis, identical twins separated from birth. Springer and Lewis were raised in entirely different household environments with no contact with each other. Both Jims had each been married twice, with first wives named Linda; their second, Betty. Their sons were named James Allan and James Alan. Each worked in law enforcement and had a dog named Toy. These striking similarities shocked the media, fascinating America with twin similarities (Segal 118). Further research at Minnesota compared twins reared apart to twins reared together, finding no significant differences in similarity. The Minnesota Study of Twins Reared Apart now includes over 135 pairs of twins or triplets ranging in age of separation, adoptive family cultures, and years before reuniting. These factors seem to have little to no impact on behavioral similarities between the twins, leading some researchers to believe that genetics have a more powerful influence. (“Nature vs. Nurture - Twin Study Overview”)