Essay On The Cell Cycle

Michael Cooney

Introduction

The cell cycle is the synchronous process by which existing cells give rise to new cells. This process can be broadly divided into two stages: interphase and mitosis. During interphase, cells increase in size, replicate their chromosomes to form sister chromatids, and increase their rates of protein synthesis. During mitosis, sister chromatids are separated and transported to opposite cell poles, followed by cell division (cytokinesis). Recent investigations have revealed much information about the morphological changes that occur in mitotic cells. These morphological changes occur in a precise order and include, in chronological order, condensation of chromosomes, changes in microtubule assembly patterns, nuclear envelope breakdown, chromosome alignment at the center of the cell, chromosome separation to opposite cell poles, and nuclear envelope reassembly prior to cytokinesis. Similar morphological changes have been observed during meiosis, indicating that the processes driving DNA distribution in somatic cells and gametes is similar (Baserga, 1968).

Though these morphological changes have been known for some time, very little is known about the mechanisms underlying them. The processes that govern cell cycle regulation are of great interest to researchers, as aberrations like improper chromosome segregation and nonfunctional microtubule assembly can result in apoptosis or, if the cell doesn’t undergo apoptosis, cancer. Most evidence surrounding cell cycle regulation comes from studies on embryonic development of amphibians. Amphibian eggs contain many of the proteins required to carry out mitosis, but can only enter mitosis after fertilization. In addition to these proteins, the eggs contain a v...

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...ty of cyclin variants with mutations in the 13-90 amino acid region to induce the transition to interphase could specifically identify the amino acids that are required for cyclin degradation, perhaps providing a clue as to the responsible mechanism.

References

1. “Biochemistry of the cell cycle: A review”, Baserga. Cell Proliferat.1(2): 167-191.

2. “The effect of protein synthesis inhibition on the entry of messenger RNA into the cytoplasm of sea urchin embryos”, Hogan and Gross. J. Cell Biol. 49(3):692-701.

3. “Accumulation of histone repeat transcripts in the sea urchin egg pronucleus”, Venezsky et al. Cell. 24(2):385-391.

4. “Role of hormones in oocyte maturation”, Schuetz. Biol. Reprod. 10(2):150-178.

5. “Cell cycle dynamics of an M-phase-specific cytoplasmic factor in Xenopus laevis oocytes and eggs”, Gerhart et al. J Cell Biol. 98(4): 1247-1255.