A twin is one of two children produced in the same pregnancy. Twins can either be identical (monozygotic) which means that they develop from one zygote that splits and forms two embryos, or they can be fraternal (dizygotic) which means that they develop from two separate eggs that are fertilized by two different sperms. Identical twins do have the same DNA, but they can be expressed in a different way. The environment the twins are exposed to determines the fine physical characteristics. Identical twins do not have the same fingerprint, and as they get older, more differences usually develop. The chance of having twins is 0.4% which is 1 in 250. Fraternal twins have an extremely small chance of having the same chromosome profile, they can look completely different then each other and they can be of the same sex or of the opposite sex. This review will detail information on how twin characteristics are genetically dispersed, or if it is due to the environment. This paper will review a number of articles, and various secondary sources published by professors, and psychologists in the field of twin studies.
Identical twins share all of their genes, while fraternal twins share only about 50% of them. So, if a researcher compares the similarity between sets of identical twins to the similarity between sets of fraternal twins for a particular trait, then the extra resemblance between the identical twins should be due to genes rather than the environment. A major assumption is that identical and fraternal twins will experience the same morals, expectations and experiences when raised together. If identical twins turn out to be more similar to each other than fraternal twins, then their same genes are the reason. People have a tendency to treat identical twins more similarly than fraternal twins because they look alike. Identical twins will also notice their own physical similarity, and might copy each other from time to time. They will most likely be...
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