Question

Fraternal twins in humans are produced when

• A. Two sperms fertilize an ovum and the first two blastomeres separate from each other
• B. One sperm fertilizes an ovum and the first two blastomeres separate from each other
• C. Egg develop parthenogenetically and first two blastomeres separate from each other
• D. Two ova are fertilized simultaneously

Answer 1

The correct option is D Two ova are fertilized simultaneously

Fraternal twins are also called as 'dizygotic'. This means there is fertilization of two seperate eggs(ova) by two individual sperms simultaneously. They are implanted in the uterine wall at the same time. They usually develop in two separate amniotic sacs. They are also called as 'biovular' since two eggs form two zygotes.
So, the correct is answer is 'Two ova are fertilized simultaneously'.