Cleavage in mammalian egg is[2000]a)superficial meroblasticb)discoidal meroblasticc)unequal holoblasticd)equal holoblasticCorrect answer is option 'C'. Can you explain this answer?

Question

Answer

The progressive division of cells during embryonic growth is called cleavage, it is not accompanied by any increase in the embryo's overall size.The first cleavage occurs in human zygote about 30 hours after fertilization. It is holoblastic (complete) and gives rise to the blastomeres-one of which is slightly larger than the other.

Answer

Unequal holoblastic because yolk sac is present in mammalian egg in small amount and unequal.

Answer

Cleavage in Mammalian Egg

Holoblastic Cleavage

- Holoblastic cleavage results in the complete division of the fertilized egg into smaller cells, resulting in the formation of a compact ball of cells known as the morula.
- In mammals, holoblastic cleavage is unequal, meaning that the cells divide at different rates and produce cells of different sizes.

Unequal Holoblastic Cleavage

- In mammals, the first cell division is symmetrical, resulting in two equally sized cells.
- However, subsequent cell divisions are asymmetrical, resulting in daughter cells of different sizes.
- This is due to the presence of yolk in the mammalian egg, which is unevenly distributed.
- The smaller cells resulting from the earlier, faster cell divisions are known as blastomeres, while the larger, slower-dividing cells are known as macromeres.

Mammalian Embryonic Development

- After the morula stage, the mammalian embryo undergoes further development, including the formation of the blastocyst, which contains an inner cell mass that ultimately gives rise to the embryo proper.
- The blastocyst also contains a layer of cells known as the trophectoderm, which forms the outer cell layer of the placenta.

Conclusion

- In summary, cleavage in mammalian eggs is unequal holoblastic cleavage, resulting in daughter cells of different sizes due to the uneven distribution of yolk.
- This process ultimately gives rise to the blastocyst, which is a key developmental stage in mammalian embryonic development.

Answer

Cleavage (embryo)
Depending mostly on the amount of yolk in the egg, the cleavage can be holoblastic (total or entire cleavage) or meroblastic (partial cleavage). The pole of the egg with the highest concentration of yolk is referred to as the vegetal pole while the opposite is referred to as the animal pole.

Answer

Cleavage in human zygote is holoblastic. It divides the  zygote and the  blastomeres completely into daughters cell. It is unequal as blastomeres is differ in size.

Top Courses for NEETView all

Biology Class 11

Daily Test for NEET Preparation

Topic-wise MCQ Tests for NEET

NEET Mock Test Series - Updated 2026 Pattern

Physics Class 11

Top Courses for NEET

Top Courses for NEET

Related Content

About NEET

NEET Preparation Material

How to Prepare for NEET Exam?

NCERT Based Study Material

NEET Mock Tests

Other Popular Exams

Company