cell cycle

cell cycle

The process of cell division in eukaryotic cells is carefully controlled. The cell cycle ( Figure 1.1) is the life cycle of an eukaryotic cell, with cell division at the end of the cycle. Like a human life cycle, which is made up of different phases, like childhood, adolescence, and adulthood, the cell cycle also occurs in a series of phases. The first cell cycle begins with the formation of a zygote from the fusion of a male and female sex cell ( gamete). The steps of the cell cycle can be divided into two main components: interphase and the mitotic phase. Interphase is the stage when the cell mostly performs its everyday functions. For example, it is when a kidney cell does what a kidney cell is supposed to do. The cell also gets ready to divide during this time. The cell divides during the mitotic phase, which consists of mitosis and cytokinesis. Most of the cell cycle consists of interphase, the time between cell divisions. Interphase can be divided into three stages: 1. The first growth phase (G1): During the G1 stage, the cell doubles in size and doubles the number of organelles. 2. The synthesis phase (S): The DNA is replicated during this phase. In other words, an identical copy of all the cells DNA is made. This ensures that each new cell has a set of genetic material identical to that of the parental cell. This process is called DNA replication. 3. The second growth phase (G2): Proteins are synthesized that will help the cell divide. At the end of interphase, the cell is ready to enter mitosis. Shown is the cell cycle. Notice that most of the cell cycle is spent in Inter- phase (G1, S, and G2). Mitosis and cy- tokinesis occur during the Mitotic phase. Some cells may enter a resting phase dur- ing which progression through the cycle stops. During mitosis, the nucleus divides as the chromosomes are equally separated. One nucleus becomes two nuclei, each with an identical set of chromosomes. Mitosis is followed by cytokinesis, when the cytoplasm divides,


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dna replication is part of the cell cycle.

-->  a. true

b. false

cell division occurs at the end of the cell cycle.

-->  a. true

b. false

during which phase of the cell cycle does the cell prepare for mitosis?

a) the first growth phase

b) the synthesis phase

-->  c) the second growth phase

d) the mitotic phase

during which phase of the cell cycle does cell division occur?

a) the first growth phase

b) the synthesis phase

c) the second growth phase

-->  d) the mitotic phase

what is the outcome of mitosis and cytokinesis?

a) two cells

-->  b) two genetically identical cells

c) two genetically identical nuclei

d) a cell ready for cell division

when does a cell have two nuclei?

a) after the g2 phase

b) after the s phase

-->  c) after mitosis

d) after cytokinesis

interphase consists of what part of the cell cycle?

a) g1, s, g2 and the mitotic phase

b) g1 and g2

-->  c) g1, s and g2

d) the s and mitotic phase

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