Proteins organize themselves to form a series of fibers called the spindle, which is involved in chromosome movement during mitosis. In the G 2 phase, the cell prepares for mitosis. Human cells contain 92 chromosomes per cell in the S phase. During this process, each chromosome is faithfully copied, so by the end of the S phase, two DNA molecules exist for each one formerly present in the G 1 phase.
In normal human cells, there are 46 chromosomes per cell (except in sex cells with 23 chromosomes and red blood cells with no nucleus and, hence, no chromosomes).ĭuring the S phase of the cell cycle, the DNA within the nucleus replicates. During the G 1 phase, each chromosome consists of a single molecule of DNA and its associated histone protein. For example, a pancreas cell in the G 1 phase will produce and secrete insulin, a muscle cell will undergo the contractions that permit movement, and a salivary gland cell will secrete salivary enzymes to assist digestion. The G 1 phase follows mitosis and is the period in which the cell is synthesizing its structural proteins and enzymes to perform its functions. The interphase stage of the cell cycle includes three distinctive parts: the G 1 phase, the S phase, and the G 2 phase. Mitosis is the phase of the cell cycle during which the cell divides into two daughter cells. During interphase, the cell spends most of its time performing the functions that make it unique. The cell cycle is generally divided into two phases: interphase and mitosis. With few exceptions (for example, red blood cells), all the cells of living things undergo a cell cycle. The cell cycle involves many repetitions of cellular growth and reproduction.
Quiz Movement through the Plasma Membrane.
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