Question

Define Cell Cycle.

Answer 1

Hint:- All organisms are composed of cells. A Cell is known as the structural and functional unit of all living organisms. Cells are of two types i.e. Prokaryotic cells and Eukaryotic cells. The pre-existing cells give rise to the new cells.

Complete Answer:- Cell division is an important process in living organisms. DNA replication and cell growth are two major factors of cell division. Cell cycle is defined as a sequence of events by which the cell 's genome divides into two daughter cells. Cell division is of two types; Mitosis and Meiosis. Cell cycle consists of two phases i.s. Interphase and Division Phase. The interphase is further divided into G1 phase or Pre DNA synthesis phase, S – phase, G2 phase or post DNA synthesis phase and G0 phase. The division phase, also known as M – phase lasts only about an hour. It represents the phase where the actual division occurs. The M-phase starts with nuclear division and ends with the division of cytoplasm. The former division is called Karyokinesis and the latter is known as cytokinesis. The M-phase has 4 stages named Prophase, Metaphase, Anaphase and Telophase.

Note:- Meiosis occurs during Gametogenesis leading to the formation of haploid gametes. Meiosis involves two sequential cycles called meiosis I and meiosis II. Meiosis I is also known as heterotypic division or reduction division as it features the reduction in chromosome number. Here, pairing of the homologous chromosomes and recombination between them occurs. The division of chromosome or centromere happens in meiosis II. Meiosis II can also be termed as homotypic division or an equational division.