Cell Cycle And Cell Division

The two cells produced from meiosis I will enter into meiosis II in which each of the cells has two chromatids. In metaphase II the centromere of the individual chromosome is attached to the two kinetochore-microtubules from either side and chromosomes are arranged in the center. In Anaphase II splitting of the centromere of each chromosome and in prophase II nuclear membranes disappear. Along with that chromosome becomes compact.

In prophase- of meiosis, the chromosomes become visible. During this phase, the chromosomes cross over at points called chiasmata.

The duration of cell cycle can vary from organism to organism and also from cell type to cell type. For example, normal human cells in culture, divide once in approximately every hours but yeast can progress through the cell cycle in only about minutes.

Metaphase is the best time to count the number and study the morphology of chromosomes. At metaphase, the condensed chromosomes with two chromatids are
arranged at the equatorial plate. Kinetochore, consisting of multilayered plates of proteins, forms on opposite sides of each centromere and becomes intimately associated with the two sister chromatids. In onion root tip, each somatic cell contains chromosomes. A cell undergoing cell division has duplicated its chromosomes thus a cell at metaphase stage of cell division has chromosomes. As each chromosome has two kinetochores thus during metaphase kinetochores can be seen.

A typical cell cycle is divided into two basic phases-Inter phase and M-phase (mitosis phase). The interphase is further divided as - phase (Gap 1), S-phase (synthesis) and -phase (Gap 2). M-phase starts after which is divided into four stages prophase, metaphase, anaphase and telophase.a