All living things go through a life cycle, including cells. The cell's life cycle is divided into two major phases:
Interphase
M phase (Mitosis)
Mitosis is further broken down into four separate phases:
Prophase
Metaphase
Anaphase
Telophase
During its life cycle, a typical cell spends most of its time in Interphase, where it grows and carries out its particular job. At some point in its life, it is triggered to divide into two daughter cells. This cell division is called mitosis, and it takes place during the last four phases of the cell life cycle: Prophase, Metaphase, Anaphase, and Telophase. The purpose of mitosis is to copy the genetic material so that when Telophase has ended, the result is two genetically identical cells. These two cells then start their own life cycle beginning with Interphase.
It is important that you understand how the cell cycle is organized. Cycles repeat the same steps over and over in the same order.
A closer look at Mitosis reveals that the first phase: Interphase, is the longest part of the life cycle in most cells. The nuclear membrane is present. Genetic material is in the form of chromatin (long, thin strands). Genetic material duplicates (doubles) during Interphase.
On to Prophase of the life cycle of a cell. During this phase the nuclear membrane disappears. Chromosomes become visible as identical pairs called chromatids. Chromatids are joined at the center by a centromere. Thin fibers form from one end of the cell to another.
Metaphase is the next phase of mitosis. The chromosomes that were paired during prophase, line up across the middle of the cell. Fibers attach themselves to the centromeres.
Anaphase follows metaphase. During anaphase, centromeres divide. Chromatids in each chromosome separate and move to the opposite ends of the cell.
Telephase is the final phase before the cell divides. The nuclear membrane reforms around each set of daughter chromosomes. The chromosomes become less visible. The cytoplasm divides (this is called cytokinesis) resulting in two identical cells. And thus the cycle begins again.
Every organism has a specific number of chromosomes in its cells. All human cells (except the reproductive cells) have 46 chromosomes or 23 pairs (one set from each parent). During mitosis, each chromosome must duplicate, so that each daughter cell gets a full set of 46 chromosomes.
We have been studying the life cycle of a cell. See what you can recall from what you have learned so far.
Question 1 of
The process by which a cell divides into two daughter cells is called…
The correct answer is e. mitosis. Interphase is the first stage of a cell's life. Mitosis is the process of cell division. Telophase, prophase, and metaphase are all specific phases of mitosis.
The correct answer is b. The daughter cells get a copy of the parent cell's DNA. When a cell divides, each of the pairs of new cells gets a copy of the parents' DNA.
The correct answer is d. Chromosomes. The chromosomes are not visible in the first part of the cell life cycle, but they are visible in the second part of the cell life cycle. The nuclear membrane and the genetic material are visible only in the first part.
The correct answer is C. They can't be replaced; damage will be permanent. Because the cells don't divide, they don't reproduce themselves. IF the cells are damaged, they will not be replaced by other nerve cells or any other kind of cell.
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