Twins

Identical twins develop from

• one egg, fertilized by one sperm
• one egg, fertilized by two separate sperm cells
• two eggs, both fertilized by the same sperm cell
• two eggs, each fertilized by a separated sperm cell

Which event would result in the production of fraternal twins?

• one egg fertilized by two sperm cells
• two egg cells fertilized by one sperm cell
• two egg cells each fertilized by separate sperm cells
• two eggs develop without fertilization

In humans, the number of sperm cells required to produce a pair of identical twins is

• 1
• 2
• 3
• 4

Identical twins develop from

• two zygotes that fuse during cleavage
• two eggs fertilized by one sperm cell
• one egg fertilized by sperm cells
• one zygote that divides into two parts

A woman gave birth to triplets, two identical girls and one boy. The number of egg cells involved would be

• 1
• 2
• 3
• 4

Identical twins would result from

• fertilization of two eggs
• eggs from the same ovary
• same zygote
• formation of different zygotes