Which one of the following statements about morula humans is correct?

Options

A. (a) It has more cytoplasm and more DNA than an uncleaved zygote
B. (b) It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA
C. (c) It has far less cytoplasm as less DNA than in an uncleaved zygote
D. (d) It has more or less equal quantity of cytoplasm and DNA as in uncleaved zygote

Answer

**Step-by-Step Solution:**

1. **Understand the Morula Stage**: The morula is a developmental stage that occurs after the fertilization of an egg by a sperm. It typically consists of 8 to 16 cells formed through the process of cleavage, which is a series of rapid mitotic divisions.

2. **Identify the Process of Cleavage**: After fertilization, the zygote undergoes cleavage, leading to the formation of a two-cell stage, followed by four cells, then eight cells, and finally the morula stage. This process does not involve growth in cell size but rather an increase in the number of cells.

3. **Analyze the DNA and Cytoplasmic Content**: During the cleavage process, while the number of cells increases, the total cytoplasmic content remains relatively constant because the cells are dividing without significant growth. However, the DNA content increases because each cell contains a complete set of DNA, which doubles with each mitotic division.

4. **Evaluate the Given Statements**:
- **Statement A**: Claims that the morula has more cytoplasm and more DNA than an uncleaved zygote. This is incorrect because the cytoplasmic content does not increase significantly, and while DNA content increases, it does not exceed that of the zygote in terms of total DNA.
- **Statement B**: States that the morula has almost equal quantity of cytoplasm but much more DNA than an uncleaved zygote. This is correct because the cytoplasmic content remains similar, but the DNA content increases due to mitosis.
- **Statement C**: Suggests that the morula has far less cytoplasm and less DNA than an uncleaved zygote. This is incorrect because the DNA content is greater in the morula.
- **Statement D**: Indicates that the morula has more or less equal quantity of cytoplasm and DNA as an uncleaved zygote. This is also incorrect since the DNA content is higher in the morula.

5. **Conclusion**: The correct statement about the morula is **Statement B**, which accurately describes the relationship between the cytoplasmic and DNA content in the morula compared to the uncleaved zygote.