Question

What is true about cleavage in the fertilized egg of a human?
A. Meroblastic
B. Starts when egg reaches uterus
C. Starts in fallopian tube
D. It is identical to normal mitosis

Answer 1

Female gamete is called an egg. When the fusion of egg and sperm occur it forms zygote. Holoblastic division occurs in the fertilized egg. It occurs in the fallopian tube. Implantation of the zygote occurs in the uterus.

Complete answer:
Female reproductive system contains ovaries, fallopian tubes, and uterus. Ovaries release eggs for the process of fertilization. Egg is the female gamete; it has a haploid number of chromosomes. When the female gamete fuses with the male gamete it forms zygote. Fusion of male and female gametes occurs in the ampullary region of the fallopian tube. Zygote has diploid number of chromosomes. Meiosis occurs at the time of gamete formation while growth and development of zygote includes the mitosis division.
The cleavage in the fertilized egg occurs in the fallopian tube. Zygote undergoes mitotic divisions (called cleavage). It occurs in the isthmus region of the fallopian tube and moves to the uterus for implantation. In humans, the egg cleavage is holoblastic. The cleavage stage embryos are known as blastomeres. Before the implantation cells undergo mitotic division in 2, 4, 8, 16, and blastocyst stages. The female reproductive part through which these cells are transferred to the uterus is the fallopian tube.
From the above information we have found that cleavage in fertilized eggs in humans starts in the fallopian tube.

Hence, the correct answer is option (C).

Note: After the blastocyst stage, the zygote attaches to the trophoblast layer of the uterus. In this way implantation of zygote occurs. Further development occurs in the uterus. Embryo gets nutrition and air through the placenta. Mitosis division occurs during this phase; it is called the post fertilization phase. Zygote has diploid number of chromosomes.