Dizygotic twins and monozygotic twins are the result of two distinct genetic processes. With dizygotic meaning fraternal and monozygotic meaning identical twins. Dizygotic twins happens when two separate eggs are fertilized by two separate sperm, this results in two distinct siblings who share 50% DNA like any other sibling. Many things can influence the likelihood of having dizygotic twins like ethnicity, maternal age, etc. Specific genes like FSHB and SMAD3 have been linked to increasing the changes of dizygotic twining. These twins can be the same or different sexes, have their own amniotic sac, and placentas.
Monozygotic twins, on the other hand, are genetically identical twins that share all of their DNA because a single fertilized egg divides into two embryos. Though the precise origin of this splitting is yet unknown, timing plays a role: early splits result in separate amniotic sacs and placentas, whereas later splits may result in shared structures that affect their development and health effects. Despite having the same appearance, monozygotic twins might differ due to epigenetic factors, which modify gene expression without changing the DNA sequence. They are crucial for comprehending how environment and genetics interact to shape human characteristics because of these minute differences.
https://medlineplus.gov/genetics/understanding/traits/twins/
https://www.webmd.com/parenting/do-twins-run-in-families-what-to-know-heredity-twins
Hey Marguerite, your post it is pretty interesting. It is worth to mention that some times Dizygotic twins can be identical too. My cousins are a set of twins which are dizygotic but are identical in aspect and sex.
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