Human Reproduction and Twin Development

What happens when a sperm successfully enters an egg?

• The egg gets bigger.

• The egg changes so no other sperm can enter.

• The sperm swims away.

• The egg turns blue.

How many chromosomes does a new baby have from both parents?

• 23

• 46

• 100

• 12

What is the special name for the very first cell of a new baby?

• A baby cell

• A zygote

• A tiny egg

• A sperm

What helps the new cell move from the fallopian tube to the uterus?

• Tiny hairs called cilia and muscle squeezes.

• The baby's kicks.

• The mother's walking.

• It floats by itself.

What is the name for when the new cell attaches to the wall of the uterus?

• Growing

• Hatching

• Implantation

• Floating

What kind of twins are formed when a fertilized egg splits very early?

• Conjoined twins

• Twins who share one placenta

• Twins who have their own placenta and amniotic sac

• Twins who share one amniotic sac

If a fertilized egg splits a little later, what do the twins share?

• Nothing at all

• One placenta, but each has their own amniotic sac

• One amniotic sac, but each has their own placenta

• All their body parts

What is Twin-To-Twin Transfusion Syndrome (TTTS)?

• When twins share a placenta and one twin gets too much blood, and the other gets too little.

• When twins are born joined together.

• When twins have separate placentas and amniotic sacs.

• When twins have different blood types.

What is a big problem for twins who share both a placenta and an amniotic sac?

• They can get their umbilical cords tangled.

• They cannot grow big enough.

• They always have different birthdays.

• They cannot share toys.

Why are some twins born joined together?

• The egg split too early.

• The egg split too late, after it was already growing.

• They had different parents.

• They were not identical twins.