Question

Name the stage in the cell cycle where DNA replication occurs.

Answer 1

DNA replication is the semi-conservative replication of DNA by biological process that creates two identical replicas of DNA from one original DNA molecule.

Complete answer:
Continuity of life is an important characteristic of living organism and is achieved through the process of reproduction, the reproduction maybe sexual or Asexual both of these involves the division and replication of cells even the growth and development of every living organism depends on the growth and the division of its cells.
There are two basic processes in cell reproduction one is cell growth and another one is cell division. These are collectively called cell cycles. Cell cycle is a sum of those events by which a cell duplicates its genome and synthesizes cell content and eventually divides into daughter cells. These events are themselves under genetic control.

Two parts of cell cycle are:

Interphase: Interface consists of G1 or Gap one or post mitotic phase, S or synthetic phase and G2 or gap

M phase: Mitotic Phase or D-phase

Stage of regulation of cell cycle

G1 phase during which a cell starts a new cycle enters the S- phase and finally divides. Once this G1 checkpoint has been passed and the cell enters the S phase, DNA replication begins thus the cell goes on to complete a new cycle. Therefore, the initiation of cell division is triggered by doubling of DNA in S- phase and hence it can be said that DNA replicates in S-phase.

Mitosis: It is also called indirect cell division and somatic cell division or equational division. It is in this where the mature somatic cell divides in such a way that chromosome number is kept constant in daughter cells as those in parent cells due to which the daughter cells are quantitatively as well as qualitatively similar in genetic material to the parental cell. This is called an equational division.
It is divided into two phases; karyokinesis or nuclear division and cytokinesis or cytoplasmic division.
Karyokinesis consists of four phases for the convenience on the basis of position and morphology of chromosome: Prophase, anaphase; metaphase and telophase.
Cytokinesis or cytoplasmic division: As the name suggests, here the division of cytoplasm into two daughter cells occurs.

Note: Few proteins play an important role in stimulating cell division. They are grouped as- growth factors, growth factor receptors, signal transducers, and nuclear regulatory proteins.
For a stimulatory signal to reach the nucleus and initiate cell division, four steps occur:
A growth factor must bind to its receptor on the cell membrane.
Second, the receptor must become temporarily activated by this binding event.
The activation must stimulate a signal to be transmitted, from the receptor at the cell surface to the nucleus within the cell.
Lastly, transcription factors within the nucleus must initiate transcription of genes involved in cell proliferation.