Here, we have a cell and it's sister cell. As you join me today on our brilliant journey of the cycle of a cell, you will see, up close, what the journey of a new cell is like. Some cells, unlike the ones we look at today, do not reproduce. Instead, they stay in a G 0 phase.There, they will stay and will live out their lives. An example of those would be human brain cells. The cells we'll be looking at today will reproduce.
Right over here, we can see the same cell has entered interphase; the longest phase in the cell cycle. The cell is entering the first phase of the interphase known as Group 1 (or G1). In this phase, the cell increases in size, produces extra organelles, and prepares for DNA synthesis. It's at this time where a cell decides weather it will enter G0 or continue on to the next phase of interphase.
Our team comes across the same cell a while later. We find the cell is now in the synthesis phase of interphase. In this phase, the cell duplicates DNA and chromosomes. At this point the cell has twice as many chromosomes (sister chromatids) and DNA...
After the cell has finished the synthesis phase, in enters G2. In this final part of interphase, the cell synthesis proteins and grows in size in preparation for the next phase; mitosis. *Directors Commentary* The microtubules in the cell reorganize and form a spindle which will be used in the next part of the cells life cycle. Also to note, cells divide because of growth, damage, or replacement.
Mitosis is the shortest phase in the cycle of a cell. Mitosis is comprised of 4 sub-phases: prophase, metaphase, anaphase and telophase. Here we see prophase and metaphase. In the prophase the centrosomes head toward opposite sides of the cell and spindle fibres begin to form. In the metaphase, the longest phase of mitosis, the chromosomes move to the centre of the cell and the spindle connects to the centromere.
In the last two parts of mitosis, anaphase and telophase, the single cell becomes two. In anaphase, the proteins that hold the chromatids together break apart and pull the chromatids towards the centrosome. In the final phase, telophase the spindles begin to disappear and membranes form two daughter nuclei. The cell now divides into two sister cells. This is cell cycle. Join us text time as our crew finds out if kids in grade 10 know this material well enough to pass.