According to wikipedia the incidence of monozygotic twins is 3/1000 births.
Furthermore, consider monosomy X or turner syndrome is the result of X or Y chromosome deletion occurring in the cell, estimated at about 1/5000 births. Secondly, consider kleinfelter syndrome, which affects about 1/1000 births.
Consider a scenario where a sperm carrying XY sex chromosomes fertilizes an egg carrying a single X chromosome, resulting in an XXY embryo. Afterwards, in our hypothetical perfect scenario, the embryo splits into monozygotic twins, after which one embryo undergoes spontaneous Y chromosomal deletion, and another embryo undergoes spontaneous X chromosomal deletion. In this scenario, a set of monozygotic twins of different sexes would be produced, who share all similar DNA save for one single X chromosome found in the female and deleted in the male.
P(child has kleinfelter) * P(child is twin) = (3/1000)(1/1000) = (3/1,000,000)
Consider that the remaining two events are independent, so: (3/(1,000,000))(1/25,000,000) = 3 in 25 trillion or 1 in 8.3 trillion births will result in a pair of monozygotic twins who differ solely by sex chromosomes. Consider that if we rearrange the events, we can change it so the female has two identical X chromosomes, thus resulting in a pair of twins of different genders who only differ by a Y chromosome or about 200 sex determining genes. Unfortunately, about 113 billion people have ever lived on Earth, meaning that in all likelihood this pair of twins has not been born yet. Yet, if they were, each would be able to exactly see what they would look like as the opposite sex, and would be able to have heterosexual sex with a clone of themselves. If they had children together, the children would be 99.99% similar to the non-kleinfelter version of the original embryo, with some changes in how many allele heterozygosity.
Furthermore, consider monosomy X or turner syndrome is the result of X or Y chromosome deletion occurring in the cell, estimated at about 1/5000 births. Secondly, consider kleinfelter syndrome, which affects about 1/1000 births.
Consider a scenario where a sperm carrying XY sex chromosomes fertilizes an egg carrying a single X chromosome, resulting in an XXY embryo. Afterwards, in our hypothetical perfect scenario, the embryo splits into monozygotic twins, after which one embryo undergoes spontaneous Y chromosomal deletion, and another embryo undergoes spontaneous X chromosomal deletion. In this scenario, a set of monozygotic twins of different sexes would be produced, who share all similar DNA save for one single X chromosome found in the female and deleted in the male.
P(child has kleinfelter) * P(child is twin) = (3/1000)(1/1000) = (3/1,000,000)
Consider that the remaining two events are independent, so: (3/(1,000,000))(1/25,000,000) = 3 in 25 trillion or 1 in 8.3 trillion births will result in a pair of monozygotic twins who differ solely by sex chromosomes. Consider that if we rearrange the events, we can change it so the female has two identical X chromosomes, thus resulting in a pair of twins of different genders who only differ by a Y chromosome or about 200 sex determining genes. Unfortunately, about 113 billion people have ever lived on Earth, meaning that in all likelihood this pair of twins has not been born yet. Yet, if they were, each would be able to exactly see what they would look like as the opposite sex, and would be able to have heterosexual sex with a clone of themselves. If they had children together, the children would be 99.99% similar to the non-kleinfelter version of the original embryo, with some changes in how many allele heterozygosity.
