There are other kinds of twins as well; for example, "mirror-image twins," "polar body twins," and "half-identical twins." These names refer to the time that the egg splits in identical twins. This essay, however, will deal with only identical and fraternal twins (5). The question now is, Are identical twins allergic to the same things? Since identical twins have exactly identical DNA, the sharing of allergies can shed some light on the role of genetics in allergies.
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. 1.1 Siamese - or - Conjoined Twins Let's answer the first question right off the bat. The terms Siamese Twins and Conjoined Twins are synonymous, 1 The term Siamese twins comes from the most famous of conjoined male twins, Chang and Eng Bunker, born in Siam of Chinese parents in 1811.
Identical twins possess exact copies of each other’s DNA, and are essentially clones of each other. As such [clones], they may help us to understand some aspects of human clones (Levick, 2004). Trends in the psychological development of twins suggest that a person’s environment influences an individual and can alter their personal growth. By further exploring the psychological impact of having an identical twin, scientists hope to discover how clones will mature. Multiple studies and observations have indicated that the varying genes and environments of each twin can influence many aspects of psychological development such as falling in love, aging, personality development, talents and abilities, body characteristics, health, and physiological responses (University of Minnesota).
Identical twins, regardless of being natural human clones with identical DNA, are separate people, with separate personalities and experiences. The relationship between an original and a clone is much like that between identical twins raised separately; they share the same DNA, but little of the same environment. This research will explore the science of twins, epigenetics and the fight to improve lives and combat disease. Identical twins do not always look alike. The identical term refers to how the twins are formed, not how they look.
Twin studies have been used to distinguish between genetic and environmental factors for many disorders in the general population including ectodermal dysplasia, Ellis-van Creveld, and anencephaly. This review focuses on genetic disorders affecting monozygotic, dizygotic, and conjoined twins to gain a better understanding of them. Many studies focus on twins because they have a nearly identical genome, which eliminates environmental factors. In case studies, the concordance rates in monozygotic twins have supported that certain disorders were caused by genetics and not the environment. The discordant values in twins will also be evaluated briefly.
Factors like diet, differences in physical activity, stress, and exposure to certain toxins can also influence the epigenome. So as monozygotic twins age their epigenomes and gene expressions end up being very different leading to two very different individuals. Introduction: Conrad H Waddington discovered the term epigenetics to describe the roles of genes in development and to solidify the fact that genes play a huge role and control development. So it was in the 1940’s that the term epigenetics was devised (Hallgrímsson & Hall, 2011; Morange, 2013). Epigenetics is known to describe the interaction between genetics and the environment around us describing the types of phenotypes during development.
Second, the ovum, if fertilized, can develop into a single embryo, which is the most common type of pregnancy in humans with about 99% of all births being singletons (1). Finally, the ovum can split into two separate halves resulting in genetically identical twins. The three types of twins previously mentioned are identical, which are created when the fertilized ovum separates into two complete, identical parts, conjoined, which occur as a result of a fertilized ovum not completing the equal separation resulting in two fetuses fused together in some way, and half-twins or polar body twins, which are made when an unfertilized ovum splits into two complete, identical parts and is then fertilized by two different sperm. The frequency of identical twins is 3.5 per 100 births (1) and the frequency of conjoined twins is 1 birth per 50,000 with only 100 known cases surviving their first year (5). There is no scientific explanation for why an ovum splits into two or more parts.
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.
Cloning is done in a couple of different ways. Artificial embryo twinning and somatic cell nuclear transfer. Artificial embryo twinning is done by mimicking the natural process of creating identical twins. In nature twins occur after fertilization when the zygote tries to divide into a two celled embryo and the two cells separate; each developing on their own person inside the womb. Though this is rare it does happen naturally and the two individuals are genetically identical.
The natural way of a clone is identical twins. In nature, twins occur just after fertilization of an egg cell by a sperm cell. Then when the fertilized egg, a zygote, tries to divide into a two-celled embryo, the two cells separate. Each cell continues dividing on its own, eventually developing into a separate individual within the mother. Another natural way of cloning is when single celled organisms, for example bacteria, produce genetically identical offspring.