up in the translation process in the ribosomes of the cell. In the translational process, the three nucleic-acid-containing codons match to a specific charged tRNA molecule so that a specific protein is made out of the messenger RNA molecule and the transfer RNA molecule. These proteins aren’t finished after translation but go through what’s called post-translational modification in order to be the finished protein necessary to engage in cellular processes.
THE CELL CYCLE The cell cycle is also referred to as the cell division cycle. It is the events that take place in the animal cell leading to DNA replication (the doubling of DNA) to ultimately produce two identical daughter cells. In cells that have a nucleus, there are three major phases of the cell cycle: interphase, mitotic phase, and cytokinesis. The cell grows and develops in interphase, building up the nutrients necessary for mitosis to occur. In mitosis, the chromosomes double in number and divide to opposite sides of the cell. During cytokinesis, the rest of the cell separates into the two daughter cells. Sometimes, the cell cycle is divided into four separate phases, known as the G1 phase or Gap 0 phase, S phase (synthesis phase), G2 phase, and M phase. The first three phases are called “interphase” and the M phase is divided into karyokinesis (which is the division of chromosomes) and cytokinesis (which is the division of the entire cell into daughter cells. Cells that do not divide and are in quiescence are said to be in the G0 phase. Interphase is the combination of the Gap 1 phase, S phase, and Gap 2 phase. The Gap 1 phase involves an increase in cell size and ends at the G1 checkpoint (which ensures that the cell is ready for DNA synthesis). In the S phase, there is DNA replication. In the Gap 2 phase, which is a gap between DNA synthesis and mitosis, the cell will continue to grow. There is a G2 checkpoint that ensures that everything is in place for mitosis. Mitosis involves the use of cellular energy to make two daughter cells. There is a metaphase checkpoint that makes sure the cell is ready to complete the cell division process.
76
