Cell cycle (Howard and Pelc, 1953) is a genetically controlled series of changes that occur in a newly formed cell. This process helps it in duplication of its contents, undergoes growth and division to produce two daughters. It consists of two states or periods, long non dividing growing I-phase and a short dividing M-phase. Both have substages. I-phase represents interphase. The regular sequence of G1, S, G2 (interphase) and M phase (mitotic phase) is called the cell cycle. Thus ‘S’ phase comes in between G1 & G2.