Free Embryonic Development MCQs with Answers

11. Suppose a human egg is fertilised by a sperm. If, immediately after fertilisation,the zygote is divided into two separate cells, then this process would result in

• A. Fragmentation
• B. Fraternal twins
• C. Identical twins
• D. Parthenogenesis

Explanation: The correct answer is identical twins. When a single zygote divides into two separate cells after fertilization, it results in identical twins, as both cells develop into genetically identical individuals. Fragmentation is unrelated to human zygote division, as it pertains to organisms that reproduce asexually. Fraternal twins result from two different eggs being fertilized by different sperm. Parthenogenesis is an asexual reproduction process that does not involve fertilization and is not relevant to human reproduction.

12. In a chick embryo, somites are formed from

• A. Dorsal mesoderm
• B. Somatic mesoderm
• C. Splanchnic mesoderm
• D. Lateral plate mesoderm

Explanation: Somites in a chick embryo arise from the paraxial mesoderm, which is a part of the dorsal mesoderm. These segmented blocks of mesoderm are critical for the development of the vertebral column, skeletal muscle, and dermis. The other options refer to different parts of the mesoderm that do not contribute to somite formation: the somatic and splanchnic mesoderm are parts of the lateral plate mesoderm, which is involved in forming the body's wall, circulatory system, and other structures.

13. In angiosperms, during the development of male gametophyte the generative cell divides and forms

• A. Two tube nuclei
• B. Four microspores
• C. Two male gametes
• D. Eight microspores

Explanation: In angiosperms, the development of the male gametophyte involves the formation of pollen grains, which contain two cells: a tube cell and a generative cell. The generative cell divides mitotically to produce two male gametes, also known as sperm cells. These sperm cells are involved in fertilization. Option C is correct because it accurately describes the division of the generative cell. Options A, B, and D describe processes or products not related to the division of the generative cell in pollen development.

14. The given diagram shows the experiment of embryonic induction performed by Spemann and Mangold.After analysing the result of experiment, the structure that was designated by Spemann asprimary organiser is the

• A. Second neural plate in recipient's embryo
• B. Dorsal blastopore lip area of donor's embryo
• C. Mesoderm opposite to dorsal blastopore lip in donor's embryo
• D. Mesoderm opposite to dorsal blastopore lip in recipient's embryo

Explanation: In Spemann and Mangold's experiment, the dorsal blastopore lip of the donor embryo was transplanted to the recipient embryo, leading to the formation of a secondary axis, including a second neural tube. This region was designated as the 'primary organizer' because it had the ability to induce the formation of new embryonic structures. The second neural plate and the mesoderm regions opposite to the dorsal blastopore lip are not the primary organizers; instead, they are structures influenced by the organizer's inductive signals.

15. A structure which is made up of both foetus and maternal tissue is known as:

• A. Placenta
• B. Umbilical cord
• C. Amnion
• D. Allantois

Explanation: The placenta is an organ that develops during pregnancy and is composed of both fetal and maternal tissue. It forms within the uterus and serves as a site of exchange between the maternal and fetal circulatory systems, facilitating the transfer of nutrients, gases, and waste products between the mother and the developing fetus. Maternal blood flows through the placenta, while fetal blood flows through the umbilical cord, allowing for the exchange of substances without direct mixing of the bloodstreams. The placenta also produces hormones that are important for maintaining pregnancy and supporting fetal development.

16. During human embryonic development, first site of RBC formation is

• A. Yolk sac
• B. Allantois
• C. Notochord
• D. Blastocyst

Explanation: In the human embryo, the first site of blood formation is the yolk sac. Later in embryonic life, the liver becomes the most important red blood cell-forming organ, but it is soon succeeded by the bone marrow, which in adult life is the only source of both red blood cells and the granulocytes.

17. Which one of the following events is likely to take place, if the nuclei from an 8- celled stage of an embryo are transplanted into enucleated eggs?

• A. Recipient egg dies
• B. Donor nuclei die in the new environment
• C. Cleavage occurs but is arrested after some time
• D. Formation of the viable embryo in the recipient eggs

Explanation: In the ideal scenario, the transplanted nuclei successfully integrate with the recipient egg's cytoplasm, leading to the formation of a viable embryo capable of further development.

18. The primary organizer during embryonic development:

• A. Drives cell division during cleavage
• B. Gives rise to extra embryonic tissues
• C. Secretes signaling molecules to influence the fate of other cells
• D. Folds inwards during gastrulation

Explanation: The primary organizer's role in initiating gastrulation is characterized by its ability to orchestrate the complex cellular movements that result in the folding inward of cells during embryonic development. This process is crucial for establishing the spatial organization and differentiation of tissues and organs in the developing embryo.

19. The extra-embryonic membrane which provides a fluid-filled environment for developing fetus is

• A. Chorion
• B. Allantois
• C. Yolk sac
• D. Amnion

Explanation: The amnion is an important extraembryonic membrane throughout development. The fluid in this sac supports and protects the fetus against mechanical shock and supplies water and other materials to the fetus.

20. A structure established between the uterine and foetal tissues for the exchange of oxygen, carbon dioxide, waste, nutrients and other materials is:

• A. Amnion
• B. Placenta
• C. Endometrium
• D. Uterus

Explanation: The placenta is defined as temporary intimate mechanical and the physiological connection between foetus and maternal tissue for the nutrition, respiration and excretion of the foetus. Human placenta consists of chorion only. The placenta is fully formed by the end of the third month and maintains pregnancy. In the placenta, the foetal blood comes very close to the maternal blood and this permits the exchange of material between the two. Food, water, mineral salt, vitamins, hormone antibodies and oxygen pass from the maternal blood into the foetal blood, and foetal metabolic waste, such as carbon dioxide, and urea, also water and hormones, pass into the maternal blood.