Identical twin result when an ovum splits into two after fertilization. They may also called single ovum or monozygotic twins. Since each containidentical sets of chromosomes, they are always of the same sex both girls or both boys.
Occasionally they maybe mirror image of each other in which case, the right side of the twin would resemble the left side of the other. There is no definite hereditary background for the occurance of single ovum twins.
The fertilization of seperate ove or of a single ovum may result in twin pregnancies, and are called double ovum, dizygotic or fraternal twins. There is a definite hereditary background in the double ovum twins. The frequency of twinning is affected by age as well as age and hereditary.
Plural births may arise from the fertilization of a single ovum or multiple ova up to the number of fetuses produced by conception. In a quintuplet pregnancy for example, three may develop from one ovum while the other two from seperate ovum. The famous Dionne quintuplets in Canada in May 1934 were all derived from the same ovum.
No comments:
Post a Comment