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

 Hint: Fraternal twins are called 'dizygotic' as well. This implies that two individual sperm are fertilized simultaneously by two separate eggs (ova). They are inserted at the same time in the uterine wall. In two separate amniotic sacs, they normally grow. Since two eggs from two zygotes, they are also called 'biovular'.

Complete step by step answer:
- When two eggs encounter two sperm in the womb, brotherly twins are formed. Each is individually fertilized, and each becomes an embryo. One egg is fertilized with identical twins by one sperm, and the embryo splits to become two at some later stage. Hence option A is incorrect.
- If the same egg were to be fertilized by different sperm, then right off the bat, 50 percent of your DNA will be different. They are also very different individuals, despite possessing the same DNA and being raised in the same environment. Hence option B is incorrect.
- Parthenogenesis is a process of reproduction in which, without being fertilized by sperm, an egg can develop into an embryo. Parthenogenesis is derived from the Greek word for "virgin birth," and it is recognized that parthenogenesis reproduces many insect species, including aphids, bees, and ants. Hence option C is incorrect.
- When two ova are simultaneously fertilized by two sperm cells, fraternal twins are produced. Fraternal twins are produced to produce two genetically unique children through the fertilization of two eggs (ova) by two sperm. Hence option D is correct.
Hence option D: Two ova are fertilized simultaneously is the correct answer.

Note: In the rare case when two ova are released simultaneously, Dizygotic (fraternal) twins are formed. Two separate sperm cells are fertilized. Each ovum that is fertilized develops into an embryo. They may be of the same sex, and they are genetically different.