Explain the difference between dizygotic and monozygotic twins.

Dizygotic (DZ) twins are also called fraternal twins. DZ twins are conceived when a woman releases more than one ovum and each is fertilized by a different sperm. DZ twins share about one half of their genes and, like other siblings, most fraternal twins differ in appearance, such as hair color, eye color, and height. Monozygotic (MZ), 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.