32. Seeing double: Twins!! Talk us through it.

Research

The topic on twins is very fascinating and beautiful. There are two ways in which twins are produced, dizygotic (DZ), and monozygotic (MZ). About two-thirds of twins are dizygotic; produced when two eggs are ovulated and fertilized by separate sperm. They are no more or less genetically similar than any other siblings and may be of different sexes. I find it fascinating that multiple ovulation can also result in triplets, quadruplets, or even greater numbers of offspring. Dizygotic twins implant separately on the uterine wall and each forms its own placenta, even though their placentas may fuse if they implant close together (Saladin et al, 2020). Monozygotic twins are produced when a single egg is fertilized and, up to 14 days later, the cell mass divides into two at the morula or embryoblast stage. When the split is early in gestation, each twin usually forms its own amnion and placenta. If it comes late, they may share a single amnion and placenta. Sadly, such twins have a high mortality rate because they become entangled in each other’s umbilical cords. Monozygotic twins that split later are at risk of developing as conjoining twins, which are fused at the head, abdomen, pelvis, or chest. Monozygotic twins are usually genetically identical and are of the same sex and nearly identical in appearance. Identical triplets and quadruplets occasionally result from the splitting of a single embryoblast (Saladin et al, 2020). Twins can very well be influenced by heredity. Women who hyper ovulate are more likely to have twins. The women can pass it down to her daughter, and the daughter’s chances of having twins will increase as well. However, it can also skip a generation.

Critical Thinking

         Fraternal twins are dizygotic twins. I am friends with two brothers, and they are fraternal twins. They do not look much alike and have very different characteristics. Despite the fact that one brother is taller, with a deeper voice, and has more facial hair, he is actually the younger brother. Like I said before, it can skip a generation. Even though neither of their children are twins, their children’s children can be twins. And although it doesn’t run in the family, there is always a possibility.

References

Saladin, K. (2020). Anatomy & Physiology: The Unit of Form and Function. (9th ed.). McGraw Hill Education