Final answer:
When twins have no more in common than other siblings, they are said to be fraternal twins or dizygotic twins. Fraternal twins occur when two separate eggs are fertilized by two separate sperm cells. Monozygotic twins or identical twins occur when a fertilized egg splits into two separate embryos.
Step-by-step explanation:
When twins have no more in common than other siblings, they are said to be fraternal twins or dizygotic twins. Fraternal twins occur when two separate eggs are fertilized by two separate sperm cells. This results in twins who are genetically similar, but not identical, as they share approximately 50% of their genetic material, just like other siblings.
On the other hand, monozygotic twins or identical twins occur when a fertilized egg splits into two separate embryos. Identical twins have the same genetic material and are essentially clones of each other.
Unlike fraternal twins, identical twins share 100% of their genetic material and are typically more physically similar to each other than other siblings or fraternal twins.