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Mixed Twins
Mixed twins are fraternal or non-identical twins born to multiracial families which differ in skin color and other traits considered to be racial features. From a biological point of view, the differences in these fraternal or dizygotic twins from two biracial parents are not surprising. In humans, a relatively small number of genes are thought to be responsible for human skin color. Different alleles or gene variants code for differences in the melanin found within the skin. Within some groups are high frequencies of dark skin alleles, while others have high frequencies of light skin alleles, for example. The parents of such twins, who are typically both of mixed race, have a combination of alleles for light and dark skin in their genome. Each sperm or egg cell possesses a random selection of genes from its mother or father. While not the most probable event, a sperm or egg may randomly acquire, for example, mostly alleles that confer light skin coloration or mostly alleles that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fraternal Twins
Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two embryos, or ''dizygotic'' ('non-identical' or 'fraternal'), meaning that each twin develops from a separate egg and each egg is fertilized by its own sperm cell. Since identical twins develop from one zygote, they will share the same sex, while fraternal twins may or may not. In rare cases twins can have the same mother and different fathers (heteropaternal superfecundation). In contrast, a fetus that develops alone in the womb (the much more common case, in humans) is called a ''singleton'', and the general term for one offspring of a multiple birth is a ''multiple''. Unrelated look-alikes whose resemblance parallels that of twins are referred to as doppelgängers. Statistics The human twin birth rate in the United States rose 76% from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
