Question

Twins are born to a family that lives next door to you. The twins are a boy and a girl. Which of the following must be true?

• A. They are fraternal twins.
• B. They were conceived through in vitro fertilization.
• C. They have 75\% identical genetic content.
• D. They are monozygotic twins.

Hint:

Different sexes = Fraternal twins. Same sex = Could be identical or fraternal.

Answer 1

The Correct Option is A

Monozygotic (identical) twins result from one fertilized egg dividing into two embryos, ensuring they are always the same sex due to their shared zygote origin. Dizygotic (fraternal) twins arise from two distinct eggs fertilized by separate sperm, meaning they can differ in sex and genetic makeup, similar to other siblings. A boy and girl twin combination is exclusively fraternal. In vitro fertilization does not dictate whether twins are monozygotic or dizygotic. A 75% genetic similarity is not a standard criterion for classifying twins.