What is true about cells during cleavage

Options

A. They move from animal pole to vegetal pole
B. They do not grow in size
C. They consume little `O_2`
D. Their divisions resemble ordinary mitosis

Explanation

### Step-by-Step Solution:

1. **Understanding Cleavage**: Cleavage is the series of rapid cell divisions that occur after fertilization, resulting in the formation of a multicellular structure from the zygote. This process leads to the formation of a morula and subsequently a blastula.

2. **Animal Pole and Vegetal Pole**: During cleavage, the zygote divides into smaller cells. The terms "animal pole" and "vegetal pole" refer to the two distinct regions of the blastula. The animal pole is where the cells are less yolk-rich and is associated with the differentiation of organs. The vegetal pole contains a larger amount of yolk.

3. **Cell Size During Cleavage**: One of the key characteristics of cleavage is that the cells do not grow in size. Instead, the original zygote divides into smaller cells (blastomeres) while maintaining the overall size of the embryo.

4. **Oxygen Consumption**: During cleavage, the cells consume more oxygen than they would during normal growth. This is because the metabolic activity increases as the cells are dividing rapidly.

5. **Comparison with Mitosis**: Cleavage is different from ordinary mitosis. While both involve cell division, cleavage divisions do not result in an increase in cell size and occur without the typical growth phase seen in mitosis. The cells formed during cleavage are not identical to the parent cell in terms of size and function.

6. **Conclusion**: The statement that is true about cells during cleavage is that they do not grow in size.

### Final Answer:
The correct statement about cells during cleavage is that they do not grow in size.

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