A Assuming the life of a cell starts as soon as cell divisio

A) Assuming the life of a cell starts as soon as cell division is completed and ends when the cell starts a new process of cellular division, how many times in a cell’s life does it replicate its DNA? Explain. B) How is DNA replication related to mitosis? C) When does a multicellular organism undergo mitosis (when it wants to reproduce, all the time, only when injured, when it’s growing, or when)?

Solution

In this case, cell\'s life is the duration between completion of one cell division and start of the next cell division. Completion of cell division indicates completion of mitosis or meiosis. Start of cell division indicates the same. Therefore, the duration between two mitotic phases or meiotic phases comprises of G1, S and G2 phases. DNA replication occurs only once during S phase. Therefore, DNA replicates once in cell\'s life time.

B. Mitosis refers to separation of homologous chromatids. The chromatids to separate, they have to be duplicated or replicated. Duplication of chromatids is nothing but DNA replication. Therefore, mitosis cannot occur without DNA replication.

C. Mitosis occurs in response to body\'s requirement for growth or repair. It occurs in somatic cells of eukaryotic organisms. Meiosis occurs in Germ cells to form gametes.