Q. The cell division that takes place in a zygote is known as
Solution:
Cleavage is a series of rapid mitotic divisions of the zygote which converts the single celled zygote into a multicellular structure called blastula. The cleavage divisions are no doubt mitotic as they produce diploid cells but they differ from typical mitosis in the following manner:
Characters
Cleavage
Normal mitosis
Site of occurrence
In zygote of parthenogenetic egg
In most of somatic cells
Interphase
of shorter period
of longer period
Growth
Does not occur
Occurs during interphase
Oxygen consumption size of daughter cells
High as is very rapid process Decreases
Low as is slow process
DNA synthesis
Faster
Slower
Nuclear cytoplasmic ratio
Increases
Remains same
| Characters | Cleavage | Normal mitosis |
|---|---|---|
| Site of occurrence | In zygote of parthenogenetic egg | In most of somatic cells |
| Interphase | of shorter period | of longer period |
| Growth | Does not occur | Occurs during interphase |
| Oxygen consumption size of daughter cells | High as is very rapid process Decreases | Low as is slow process |
| DNA synthesis | Faster | Slower |
| Nuclear cytoplasmic ratio | Increases | Remains same |