8Mirror-Image Twins and Semi-Identical Twins
As the name implies, mirror-image twins, also known as mirror twins, are basically the mirror images of the other. It means that their teeth would grow in opposite parts of the mouths, their hair would fall in contrasting directions, as well as their freckles or birthmarks are also on the opposite side of the bodies. In addition, their dominant hands can be different. This phenomenon occurs when an egg splits 7 to 12 days after the fertilization. During this extra period, the egg may have enough time to develop a left and right side. [9]
Semi-identical twins are a new form first reported in 2006. It was described as an unspecified set of twins between fraternal and identical. This means they are only identical on the mother’s side, but only have half of chromosomes from the father. It tends to occur when a single egg is fertilized by two sperm to form a triploid. This triploid will split later. [10]
