Cell Cycle and Cell Division Test - 6

The most common material used for study of mitosis cell division in class room is onion root and broad bean root tip. They can be grown quickly and in all seasons. Also they are esier to handle with and divisional stages are completed quickly.

A disturbance in the nucleoplasmic ratio will cause the cell to divide and attain stable ration which is 1. If it is less or more than 1 the cell becomes unstable and divides agin.

Regeneration is the ability of organism to regain its lost body parts. Regeneration is achieved by mitotic cell division to maintain same number of chromosomes in the cell.

Meiosis cell division consists of two phases. First phase is called meiosis I during which number of chromosome reduce to half the number in parent cells. In meiosis II chromosome number remain same.

Interkinesis is the stage connecting meiosis I and meiosis II cell division. It is a brief period between two stages. No DNA synthesis occurs during this period. The cellundergoes preparation for next divisional stages.

Chromosome appeared beaded during leptotene stage of prophase of meiosis I due to the distinct appearance of nucleosomes. Chromatin materials start condensing after that stage.

Chismata is formed due to  crossing over. During diakinesis of prophase I of meiosis terminalisation of chiasmata takes place which indicates end of crossing over and separation of the non-sister chromatids

Crossing over is the exchange of genetic material between non-sister chromatids of two homologous chromosomes involved in the pairing process.

Meiosis cell division is involved in gametes formation as gametes contain half the number of chromosomes that a normal cell diploid cell contains. Gametes fuse to produce diploid zygote.