Читать книгу Lifespan Development - Tara L. Kuther - Страница 108

1 What do you think about parents choosing the sex of their children? In your view, under what conditions is sex selection acceptable?

2 If you were able to selectively reproduce other characteristics, apart from sex, what might you choose? Why or why not?

Monozygotic (MZ) twins, or identical twins, originate from the same zygote, sharing the same genotype with identical instructions for all physical and psychological characteristics. MZ twins occur when the zygote splits into two distinct separate but identical zygotes that develop into two infants. It is estimated that MZ twins occur in 4 of every 1,000 U.S. births (American College of Obstetricians and Gynecologists & Society for Maternal-Fetal Medicine, 2014). The causes of MZ twinning are not well understood. Temperature fluctuations are associated with MZ births in animals, but it is unknown whether similar effects occur in humans (Aston, Peterson, & Carrell, 2008). In vitro fertilization and advanced maternal age (35 and older) may increase the risk of MZ twins (Knopman et al., 2014).

Monozygotic, or identical, twins share 100% of their DNA.

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