Fraternal twinning occurs when?

Fraternal twinning occurs when?

• A. A single zygote splits into two embryos
• B. Two ova fertilized by the same sperm
• C. Two different ova fertilized by two different sperm
• D. A zygote fails to divide

Answer: (C)

Fraternal twinning occurs when two separate eggs are released and each is fertilized by a different sperm, producing two genetically distinct zygotes. Because the eggs come from the same mother but are fertilized independently, the resulting twins are like ordinary siblings—they can be different sexes and have varying appearances. Often each zygote implants with its own placenta and amniotic sac, though placental sharing can occur in some cases depending on timing. This contrasts with identical twins, which arise from a single fertilized egg that splits into two embryos, and with a zygote that fails to divide, which would result in a single offspring. So the hallmark of fraternal twinning is two different eggs fertilized by two different sperm.

Fraternal twinning occurs when two separate eggs are released and each is fertilized by a different sperm, producing two genetically distinct zygotes. Because the eggs come from the same mother but are fertilized independently, the resulting twins are like ordinary siblings—they can be different sexes and have varying appearances. Often each zygote implants with its own placenta and amniotic sac, though placental sharing can occur in some cases depending on timing. This contrasts with identical twins, which arise from a single fertilized egg that splits into two embryos, and with a zygote that fails to divide, which would result in a single offspring. So the hallmark of fraternal twinning is two different eggs fertilized by two different sperm.